The Doctor is the central fictional character in the long-running BBC television science-fiction series Doctor Who, and also featured in a vast range of spin-off novels, audio dramas and comic strips connected to the series.

This article is specifically about the character of the Doctor. For a more general overview of the series, please see the main Doctor Who article. For more about the production history of the show, please see History of Doctor Who.

To date, ten actors have played the role in the television series, with these changes being explained by his ability to regenerate. Several other actors, and several others have played the character on stage and film, in audio dramas, and in occasional special episodes of the series. David Tennant currently portrays the tenth incarnation of the Doctor.

Who is the Doctor?

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The Doctor is a Time Lord, an extraterrestrial from the planet Gallifrey, who wanders time and space in an internally vast time machine called the TARDIS — Time And Relative Dimension (or Dimensions) In Space. Although the TARDIS once had the ability to disguise itself according to its environment, after landing in 1963 London its exterior form became "stuck" in the form of a British police box; due to a malfunctioning chameleon circuit, it has remained in that shape ever since. Though over the course of the series the Doctor occasionally attempted to fix the circuit, he eventually gave up the effort out of fondness for the police box shape. The discrepancy between the small exterior of the ship and its vast interior is explained by its dimensionally transcendental nature, whereby the ship's interior and exterior dimensions exist independently of each other.

For the most part — often due to the age and unreliability of the TARDIS's navigation system — the Doctor explores the universe at random, using his extensive knowledge of science and technology to avert whatever crises he encounters. The Doctor generally travels with one or more Doctor Who companions. Most of these choose to travel with him, while others are accidental passengers.

Although Time Lords resemble humans, their physiology differs in some key respects; like other members of his race, the Doctor has two hearts, a "respiratory bypass system" that allows him to go without air for some while, and on occasion he exhibits a super-human level of strength and stamina. He has exhibited a certain affinity towards time, as well as some limited telepathic abilities. The Doctor also exhibits some weaknesses uncommon to humans; in The Mind of Evil (1971) he claimed that a tablet of aspirin could kill him.

In his final serial, the Second Doctor stated that Time Lords could live forever, "barring accidents." When accidents do occur, Time Lords can regenerate into new bodies, resulting in extremely long life-spans.

Although a key premise in the 1996 Doctor Who television movie was that the Doctor was half-human, this detail causes a great deal of debate among fans (see below).

In the beginning

The character was first portrayed by William Hartnell in 1963, who played him as an irascible, grandfatherly figure. When, after three years, Hartnell left the series due to ill health, the role was handed over to respected character actor Patrick Troughton. To date, ten actors have portrayed distinct incarnations of the Doctor on television. (Due to Hartnell's death in 1975, actor Richard Hurndall replaced him as the First Doctor in 1983's The Five Doctors.) Of those, the longest-lasting and perhaps the most recognisable incarnation is the Fourth Doctor, as played by Tom Baker. Currently, the Tenth Doctor is portrayed by David Tennant; he inherited the role on 18 June 2005, during the final scenes of the episode The Parting of the Ways.

When the series began in 1963, nothing at all was known of the Doctor: not even his name (the actual form of which remains a mystery). In the very first serial, An Unearthly Child, two teachers from the Coal Hill School in London, Barbara Wright and Ian Chesterton, became intrigued by one of their students, Susan Foreman, who exhibited high intelligence and unusually advanced knowledge. Trailing her to a junkyard at 76 Totter's Lane, they encountered a strange old man and heard Susan's voice coming from inside what appeared to be a police box. Pushing their way inside, the two found that the exterior was actually camouflage for the dimensionally transcendental interior of the TARDIS. The old man, whom Susan called "Grandfather" but who identified himself as "the Doctor", subsequently whisked them away on an adventure in time and space.

Becoming "involved"

The Doctor is an adventurer and a scientist with a strong moral sense. He usually solves problems with his wits rather than with force, and is more likely to wield a sonic screwdriver than a gun.

As a time traveller, the Doctor has been present at or directly involved in countless major historical events on the planet Earth and elsewhere — sometimes more than once. In the 2005 series premiere, Rose, it is revealed that the Ninth Doctor was instrumental in preventing a family from boarding the Titanic prior to her fateful voyage. In The End of the World the Doctor claimed to have been on board and survived the Titanic's sinking to find himself "clinging to an iceberg."

Many historical figures on Earth have also encountered the Doctor. In City of Death it was revealed that the Doctor had met Leonardo da Vinci and William Shakespeare and that the first folio of the latter's Hamlet was transcribed by the Doctor himself. In Timelash, he met a young H. G. Wells, Albert Einstein in Time and the Rani, and Marco Polo was the subject of an adventure of the same name during the first season. More recently, the Doctor has shared adventures with Charles Dickens (The Unquiet Dead), Queen Victoria (Tooth and Claw) and Madame de Pompadour (The Girl in the Fireplace).

It is this penchant for becoming "involved" with the universe — in direct violation of official Time Lord policy — that has caused to the Doctor to be labeled a renegade by the Time Lords. Most of the time, however, his actions are tolerated, especially given that he has saved not just Gallifrey, but the universe, several times over. The Time Lords were also partial to sending him on missions when deniability or expendibility was needed. The Doctor's standing in Time Lord society has waxed and waned over the years, from being a hunted man to even being appointed Lord President of the High Council (an office he did not assume for very long and eventually was removed from in his absence). However, some Time Lords respect him to some degree for his heroic deeds. This included even the Master, who, when told in the episode The Five Doctors of a crisis threatening the Doctor's existence in the timestream, noted with concern, "A cosmos without the Doctor scarcely bears thinking about." In the end, though, the Doctor has always seemed quite content to remain a renegade and an exile. Ultimately, the Doctor found himself, by the time of his ninth incarnation, the last known surviving Time Lord following a time war.

"Doctor who?"

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In the first episode, Barbara addresses the Doctor as "Doctor Foreman", as this is the surname the Doctor's granddaughter Susan goes by, and the junkyard in which they find him bears the sign "I.M. Foreman". When addressed by Ian with this name in the next episode, the Time Lord responds, "Eh? Doctor who? What's he talking about?" Later, when he realises that "Foreman" is not the Doctor's name, Ian asks Barbara, "Who is he? Doctor who?"

Similarly, in the 2005 series premiere, Rose, when asked his name, the Doctor replies, "Just 'the Doctor'." New companion Rose Tyler later finds a website devoted to the Doctor on the Internet, run by a conspiracy theorist who has been tracking the Ninth Doctor's appearances throughout history, carrying the title "DOCTOR WHO?" (see Doctor Who tie-in websites). The BBC launched a "real" version of this website at "WHO IS DOCTOR WHO?", with the conceit that it is run by Mickey Smith, Rose's boyfriend (having taken over the site following the death of its originator).

Although listed in the on-screen credits for nearly twenty years as "Doctor Who" or "Dr. Who", the Doctor is never really called by that name in the series, except in that same tongue-in-cheek manner (for example, in The Five Doctors when one character refers to him as "the Doctor", another character asks, "Who?"). The only real exception is the computer WOTAN in the serial, The War Machines, which commands that "Doctor Who is required." As a matter of continuity, some fans believe that the computer in question was simply misinformed — it also claimed the Doctor was human. The Third Doctor's automobile, dubbed "Bessie", carried the licence plate WHO 1, the only ongoing reference to the "Doctor Who" enigma in the original series. (The Third Doctor also later drove an outlandish vehicle called the "Whomobile". However, this name was only applied to it in publicity and it is never referred to as such in the series, being simply known as "the Doctor's car".) "Doctor Who" is also used in the title of the serial Doctor Who and the Silurians, but this was a captioning mistake and not an in-story mention. The only other time this occurs is in the title of Episode 5 of The Chase: "The Death of Doctor Who".

Some fans have speculated, from the fact that the full name of the Time Lady Romana is Romanadvoratrelundar, that the first syllable of the Doctor's true name is "Who". It should be noted that, although it is often asserted that "Doctor Who" is not the character's name, there is nothing in the series itself that actually confirms this.

In The Girl in the Fireplace (2006), Madame de Pompadour reads the Doctor's mind and remarks about his name, "Doctor who? It's more than just a secret, isn't it?" In the commentary, writer Steven Moffat suggests that, as the Doctor does not tell even his closest companions his name, there must be a "dreadful secret" about it.

Alias the Doctor

Quite apart from his name, why the Doctor uses the title of "The Doctor" has never been explained on screen. The Doctor has said that he is not a medical doctor, but occasionally does show medical knowledge and stated that he studied under Joseph Lister and Joseph Bell on separate occasions. He has also been mocked by his fellow Time Lords for adhering to such a "lowly" title as "Doctor".

The Telos novella Frayed by Tara Samms (which takes place prior to "An Unearthly Child") has the First Doctor being given that title by the staff of a besieged human medical facility on the planet Iwa, suggesting at the end that the Doctor liked the official title so much that he adopted it. However, this does not quite explain why the Time Lords use the same title in addressing him. The same story also has Jill, a young girl living in the facility, naming the Doctor's granddaughter "Susan" after Jill's mother. The canonicity of all non-television sources is unclear.

To make up for his lack of a practical name, the Doctor often relies upon convenient pseudonyms. In The Gunfighters, the First Doctor uses the alias Dr. Caligari. In The Highlanders the Second Doctor assumes the name of "Doctor von Wer" (a German approximation of "Doctor Who"), and signs himself as "Dr. W" in The Underwater Menace. In The Wheel in Space, his companion Jamie McCrimmon, reading the name off some medical equipment, tells the crew of the Wheel that the Doctor's name is "John Smith". The Doctor subsequently adopts this alias several times over the course of the series, often prefixing the title "doctor" to it. The Eighth Doctor briefly used the alias "Dr. Bowman" in the 1996 Doctor Who television movie.

In The Empty Child (2005), for want of a better name, Rose introduces the Doctor to Jack Harkness as "Mr. Spock". (According to the DVD commentary for this episode, the Doctor was originally to have responded "I'd rather have Doctor Who than Star Trek" which would have been the first direct use of the Doctor Who name by the Doctor himself.) In New Earth, it is implied that the Doctor is part of the prophecy of the Face of Boe and is referred to as "The Lonely God". In Tooth and Claw, having landed in Scotland, the Tenth Doctor introduces himself as "Dr. James McCrimmon" from the township of Balamory. Later in that episode, the Doctor is knighted by Queen Victoria as "Sir Doctor of TARDIS".

To his greatest enemies, the Daleks, the Doctor is known as the Ka Faraq Gatri, the "Bringer of Darkness" or "Destroyer of Worlds". This is first mentioned in the novelisation of Remembrance of the Daleks by Ben Aaronovitch and subsequently taken up in the spin-off media, particularly the Virgin New Adventures books and the Doctor Who Magazine comic strip. In The Parting of the Ways, the Doctor claims that the Daleks call him "The Oncoming Storm" — this name is used by the Draconians (whose word for it is "Karshtakavaar") to refer to the Doctor in the Virgin New Adventures novel Love and War by Paul Cornell.

The series has also occasionally toyed with the Doctor's identity (or lack thereof). In the first episode of The Mysterious Planet, the Doctor is about to give a name after the title "Doctor..." but is interrupted. In The Armageddon Factor, the Time Lord Drax addresses the Fourth Doctor as "Thete", short for "Theta Sigma", apparently an Academy nickname (or perhaps an achieved grade). In Remembrance of the Daleks the Seventh Doctor produces a calling card with a series of pseudo-Greek letters inscribed on it (as well as a stylised question mark). This may be a reference to Terrance Dicks' and Malcolm Hulke's book The Making of Doctor Who (1972), which claims that the Doctor's true name is a string of Greek and mathematical symbols.

The question mark motif was common throughout the eighties, in part as a branding attempt. Beginning with season eighteen, the Fourth through Seventh Doctors all sported costumes with a question mark motif (usually on the lapels, except in the Seventh Doctor's case on his pullover and the shape of his umbrella handle). In the 1988 serial Remembrance of the Daleks, the Seventh Doctor was asked to sign a document, which he did using a question mark.

On-screen credits

In the early years of the spin-off comic strips, books, films and other media, the character was initially called "Doctor Who" (or just "Dr. Who") in the stories as a matter of course. This usage declined as the years went by.

Perhaps complicating the matter is that, from the first television serial through to Logopolis (the last story of Season 18 and also of the Tom Baker era), the lead character was credited as "Doctor Who" (or sometimes "Dr. Who"). Starting from Peter Davison's first story, Castrovalva (the first story of the series' Season 19) to the end of Season 26, he is credited simply as "The Doctor".

This format is continued in the 1996 television movie for Paul McGann's credit, while Sylvester McCoy's incarnation is credited as "The Old Doctor". For the 2005 revival starring Christopher Eccleston, the credit reverted to "Doctor Who". However, in The Christmas Invasion, and subsequent stories featuring David Tennant, the character is once again referred to in the closing credits as "The Doctor". According to Doctor Who Magazine #367 this reversion was specifically requested by Tennant.

Changing faces

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The changing of actors playing the part of the Doctor is explained within the series by the Time Lords' ability to regenerate after suffering mortal injury, illness, or old age. The process repairs and rejuvenates all damage, but as a side-effect it changes the Time Lord's physical appearance and personality semi-randomly. This ability was not introduced until producers had to find a way to replace the ailing William Hartnell with Patrick Troughton and was not explicitly called "regeneration" until Jon Pertwee's transformation to Tom Baker at the climax of Planet of the Spiders (1974). On screen, the transformation from Hartnell to Troughton was called a "renewal" and from Troughton to Pertwee a "change of appearance".

The original concept of regeneration or renewal was that the Doctor's body would rebuild itself in a younger, healthier form. The Second Doctor was intended to be a literally younger version of the First; biological time would turn back, and several hundred years would get taken off the Doctor's age, rejuvenating him. In practice, however, after the Doctor stated his age in the Second Doctor serial The Tomb of the Cybermen (1967), the Doctor's age has been recorded progressively, however many regenerations the Doctor goes through (but see below). Coincidentally or otherwise, the general trend has been toward increasingly younger actors for the role.

The actors who played the Doctor in the series, and the dates of their first and last regular television appearances in the role, are:

1. First Doctor - William Hartnell: (November 23, 1963–October 29, 1966)
2. Second Doctor - Patrick Troughton: (November 5, 1966–June 21, 1969)
3. Third Doctor - Jon Pertwee: (January 3, 1970–June 8, 1974)
4. Fourth Doctor - Tom Baker: (December 28, 1974–March 21, 1981)
5. Fifth Doctor - Peter Davison: (March 21, 1981–March 16, 1984)
6. Sixth Doctor - Colin Baker: (March 16, 1984–December 6, 1986)
7. Seventh Doctor - Sylvester McCoy: (September 7, 1987–December 6, 1989 in the series, and May 27, 1996, in the Doctor Who television movie)
8. Eighth Doctor - Paul McGann: (May 27, 1996, in the Doctor Who television movie).
9. Ninth Doctor - Christopher Eccleston: (March 26, 2005–June 18, 2005)
10. Tenth Doctor - David Tennant: (June 18, 2005–present)

Although throughout his regenerations the Doctor remains essentially the same person, each actor has purposely imbued his incarnation of the role with distinct quirks and characteristics. Each incarnation is therefore distinguished by appearance and behavior alike. For example, to contrast with the First Doctor's impish, grandfatherly figure, the Second Doctor was played as a superficially warm and bumbling character hiding a deeply calculating mind. The Third Doctor made the best of his Earth exile as a swashbuckling dandy; the Fourth Doctor basked in freedom with his more bohemian manner. After the sensitive, vulnerable Fifth Doctor, the Sixth asserted himself as a flamboyant blowhard. The Seventh Doctor was at first clownish, then later darker and more manipulative; the Eighth was more of a Byronesque figure, possessed of an infectious enthusiasm about the universe.

The Ninth Doctor was an enigmatic figure, impulsive and almost manic on the surface yet hiding a deep sadness and loneliness. He had a colder, less forgiving personality, perhaps hardened by the Time War that destroyed Gallifrey and left him the last of the Time Lords sometime prior to his introduction. He was haunted by his actions during the War, in which he was responsible for the destruction of ten million Dalek warships, an action that apparently also destroyed the Time Lords.

Thus far, the Tenth Doctor is lighter and more easygoing than his predecessor, both flippant and energetic, but still quick to anger when he perceived an injustice. He is also more gregarious, being friendlier with Rose's friends and family than his predecessor.

Despite his personality changes, however, the Doctor remains at his core a heroic figure, fighting the evils of the universe as he encounters them, even if his values and motives are sometimes alien.

Different actors have used different regional accents in the role. The first six Doctors spoke in Received Pronunciation or "BBC English", as was standard on British television at the time. Sylvester McCoy used a very mild version of his own Scottish accent in the role, and Paul McGann spoke with a faint Liverpudlian lilt. Only rarely, as in the case of the Eighth Doctor, who was identified as "British", or the Ninth, whose accent was clearly described as "Northern", was this ever addressed in the series. Though David Tennant speaks with a Scottish accent, he plays the Doctor with an Estuary/Cockney accent. According to producer Russell T. Davies, this was intended as a consequence of spending so much time with Rose. The Christmas Invasion would have alluded to this, but the line was cut.

Changing fashions

The Doctor's clothing has been equally distinctive, from the distinguished Edwardian suits of the First Doctor to the Second Doctor's rumpled, Chaplinesque attire to the frills and velvet of the Third Doctor's era. The Fourth Doctor's long waistcoat and trailing scarf added to his bohemian image; the Fifth's cricketer's outfit suited his youthful, aristocratic air (with a stick of celery on the lapel for an eccentric touch); and the Sixth's multicoloured jacket, with its cat-shaped lapel pins, reflected the excesses of 1980s fashion. The Seventh Doctor's outfit was more subdued — in later seasons, as his personality grew more mysterious, his jacket, tie, and hatband all grew darker.

Throughout the 1980s, question marks formed a constant motif, usually on the shirt collars or, in the case of the Seventh Doctor, on his sleeveless jumper and the handle to his umbrella. The idea was grounded in branding considerations, as was the movement starting in Tom Baker's final season toward an unchanging costume for each Doctor, rather than the variants on a theme employed over the first seventeen years of the program. When the Eighth Doctor regenerated, he clad himself in a 19th century frock coat and shirt, reminiscent of the out-of-time quality of earlier Doctors and emphasising the Eighth Doctor's more Romantic persona.

In contrast to the more flamboyant costumes of his predecessors, the Ninth Doctor wore a nondescript, worn black leather jacket, V-neck jumper and dark trousers. Eccleston stated that he felt that such definitive "costumes" were passé and that the character's trademark eccentricities should show through their actions and clever dialogue, not through gimmicky costumes. Despite this, there is a running joke about his character that the only piece of clothing he changes is his jumper, even when trying to "blend into" an historical era. The one exception, a photograph of him taken in 1912, wearing period clothing, resembles the style of the Eighth Doctor; some speculate that this may have been immediately after his regeneration, when he was still wearing his predecessor's clothes.

When, at the end of the 2005 series, the Doctor regenerated into his tenth incarnation, he briefly remained in the Ninth Doctor's attire. By the end of his first adventure, however (The Christmas Invasion), he had chosen a new outfit from the TARDIS wardrobe: a brown pinstriped suit with tie, a tan ankle-length coat and Converse Chuck Taylor sneakers, the latter calling to mind the foot-sense of his fifth incarnation.

Transitions

Save for the off-screen transition between the Eighth and Ninth Doctors, to date each regeneration has been worked into the continuing story. Also, most regenerations (save the Second-to-Third and Eighth-to-Ninth transitions) have been portrayed on-screen, in a symbolic handing over of the role. The following list details the manner of each regeneration:

1. First Doctor: apparently succumbed to old age, steadily growing weaker throughout The Tenth Planet and collapsing at the serial's end. Although the writer's intent was that this was due to the energy drain from the planet Mondas, this was not made clear in the transmitted story.
2. Second Doctor: a forced regeneration and exile to Earth by the Time Lords in the closing moments of The War Games.
3. Third Doctor: radiation poisoning from the Great One's cave of crystals at the end of Planet of the Spiders.
4. Fourth Doctor: fell from the Pharos Project radio telescope in Logopolis.
5. Fifth Doctor: spectrox toxaemia, contracted near the start of The Caves of Androzani.
6. Sixth Doctor: suffered unspecified injuries when the Rani attacked the TARDIS and caused it to crash land at the start of Time and the Rani.
7. Seventh Doctor: died on the operating table while undergoing surgery in the 1996 television movie.
8. Eighth Doctor: not revealed as yet.
9. Ninth Doctor: cellular degeneration caused by absorbing the energies of the space time vortex from Rose, which she in turn had absorbed through the heart of the TARDIS in The Parting of the Ways.

In the original series, with the exception of the change from Troughton to Pertwee, regeneration usually occurred immediately following the "death" of the previous Doctor. The changeover from McCoy to McGann was handled differently, with the Doctor actually dying and being dead for quite some time before regeneration occurred. The Eighth Doctor comments at one point that the anesthesia interfered with the regenerative process, and that he had been "dead too long," accounting for his initial amnesia.

The 2005 series began with the Ninth Doctor already regenerated, with no explanation given. In his first appearance in Rose, the Doctor looked in a mirror and commented on the size of his ears, suggesting that the regeneration may have happened shortly prior to the episode. However, the Ninth Doctor's appearances in old photographs, without being accompanied by Rose, may also suggest that he had been regenerated for some time. Russell T. Davies, writer/producer of the new series, stated in Doctor Who Magazine that he has no intention of showing the regeneration in the series, and that he believed the story of how the Eighth Doctor became the Ninth is best told in other media. In Doctor Who Confidential Davies revealed his reasoning that, after such a long hiatus, a regeneration in the first episode would not just be confusing for new viewers but also lack dramatic impact, as there would be no emotional investment in the character before he was replaced.

Eccleston stepped down from the role at the end of the 2005 series, and the Ninth Doctor regenerated into the Tenth in The Parting of the Ways. It remains to be seen whether the Ninth Doctor will appear again, although Russell T. Davies has stated that he does not intend to bring back former Doctors.

The Doctor's regenerations

It was established in The Deadly Assassin (1976) that a Time Lord can regenerate twelve times before permanently dying, for a total of thirteen incarnations. In the 1996 television movie the Eighth Doctor explicitly said that a Time Lord has "thirteen lives". In The Christmas Invasion it was stated the regenerative cycle creates a large amount of energy that suffuses the Time Lord's body. As demonstrated by the Tenth Doctor for the first time in that story, in the first fifteen hours of regeneration this energy is enough to even rapidly regrow a severed hand.

The Doctor's regenerations are usually as a result of his previous incarnation sustaining mortal injury or (in one case) having the regeneration forced on him by the Time Lords. Other Time Lord regenerations, like Romana's, have not been as dramatic or painful.

The Doctor frequently experiences a period of instability and partial amnesia following regeneration. Some post-regeneration experiences have been more difficult than others. In particular, the Fifth Doctor began reverting to his previous personalities and required the healing powers of the TARDIS's "Zero Room" to recuperate (Castrovalva). The Sixth Doctor experienced extreme paranoia and flew into a murderous rage, nearly killing his companion (The Twin Dilemma). The Eighth Doctor not only experienced amnesia, but some fans attribute his romantic actions towards his companion to post-regeneration trauma (1996 Doctor Who television movie).

The regeneration from the Ninth to the Tenth Doctor at first seemed smooth, with the Doctor regenerating standing up for the first time (The Parting of the Ways). However, shortly afterwards he began to experience spasms and became somewhat manic, frightening Rose as he pushed the TARDIS to dangerous extremes (Children in Need Special). After crash-landing the TARDIS, the Doctor collapsed and remained unconscious for most of the next fifteen hours (The Christmas Invasion). The experience was traumatic enough to cause one of his hearts to temporarily stop beating.

As noted above, the newly regenerated Tenth Doctor was able to regrow his hand when it was severed at the wrist during a swordfight with the Sycorax leader. This ability had never been exhibited before, but no previous Doctor had ever suffered an injury of this nature so soon after regeneration (although Romana did exhibit some degree of control over her regenerative process). The Tenth Doctor's lack of reaction to the injury may also point to increased pain tolerance during this period, although humans do not always register pain immediately after losing a limb, due to the effects of shock.

The TARDIS also appears to aid in the regenerative process. The Second Doctor, in The Power of the Daleks, described his renewal as a function of the ship, stating that "without it, ^* couldn't survive." Of the four occasions the Doctor regenerates outside the TARDIS, one was forced on him by the Time Lords (The War Games), one required a Time Lord to give the Doctor's cells a "little push" to start the process (Planet of the Spiders), one needed the TARDIS Zero Room to help him recover (Castrovalva) and the last occured a few hours after he had actually "died" (The 1996 television movie). That last regeneration remains the only that takes place significantly far away from the TARDIS, without any obvious interaction from any Time Lords.

Continuity curiosities

In the early serial The Edge of Destruction, it appeared that the First Doctor only had a single heart. To rectify the apparent inconsistency, a commonly held piece of fan continuity (referenced in the novel The Man in the Velvet Mask by Daniel O'Mahony) is that Time Lords only grow their second heart during their first regeneration. In The Christmas Invasion, one of the Doctor's hearts temporarily stops beating due to intense trauma; this may or may not explain the First Doctor's situation.

Also during his first regeneration, and for similarly unclear reasons, the Doctor's clothes changed along with his body (The Power of the Daleks); on all subsequent regenerations, the new Doctor generally continues to wear the clothing of his predecessor until he selects a new outfit.

In The Brain of Morbius (produced shortly before Assassin), visual images displayed during a mental battle between the Fourth Doctor and Morbius can be taken as implying that the Doctor had at least eight incarnations prior to the First Doctor. However, multiple dialogue references throughout the series (particularly in The Three Doctors, Mawdryn Undead and The Five Doctors) contradict this, as well as the fact that the Doctor has regenerated six times since then (as stated in School Reunion). Explanations have included theories that the images were of Morbius's previous incarnations (two images that are certainly Morbius also appear, and the game seems to have a symmetrical arrangement). Alternatively, they may have been false images induced by the Doctor. The Doctor Who novels have suggested that these may have been faces of the Other, a figure from Gallifrey's ancient past and the genetic predecessor of the Doctor (although being from the tie-in novels, the canonicity of this character is debatable).

In the Sixth Doctor story arc The Trial of a Time Lord, a Time Lord with the title of the Valeyard (played by Michael Jayston) was revealed to be a potential future Doctor, existing somewhere between his twelfth and final incarnations and embodying all the evil and malevolence of the Doctor's dark side. The Valeyard was defeated in his attempt to actualize himself by stealing the Sixth Doctor's remaining regenerations, however, and so may never actually come to exist.

The idea of an "in-between" version of the Doctor has its precedents. In Planet of the Spiders, a Time Lord's future self (described as a "distillation" of the future incarnation) was shown to exist as a corporeal projection that assisted his then-current incarnation. In Logopolis, a mysterious white-cloaked figure known as the Watcher assisted in the transition between the Fourth and Fifth Doctors. Nyssa commented that the Watcher "was the Doctor all the time," but there is no real evidence to back up this assertion and the actual nature of the character has never been made clear.

Perhaps the most controversial element from the 1996 television movie was the revelation that the Doctor is half-human ("on ^* mother's side"). One possibility is that the Doctor was joking. However, the Doctor's half-human nature is used to explain how he can access the Eye of Harmony, which in the movie requires a human eye, and is mentioned by the Master. Another possibility is that only the Eighth Doctor was half-human due to the particularly traumatic circumstances of his regeneration, rather than the Doctor having been half-human all along. If so, it is unclear how he could specifically be half-human on his mother's side.

The Time Lord ability to change species during regeneration is referenced by the Eighth Doctor in relation to the Master in the television movie, and is supported by Romana's regeneration scene in the 1979 serial Destiny of the Daleks. The Daleks also implied during the events of The Daleks' Master Plan (1965-66) that the First Doctor's humanoid form is not his actual appearance. The new series has not made any allusions to mixed parentage, simply referring to the Doctor as "alien". However, the trade paperback Doctor Who: The Legend Continues by Justin Richards, published to coincide with the new series, refers to the Doctor as half-human.

The spin-off novels have also tried various methods to explain this revelation, suggesting that the Doctor retained some human DNA from his time as Dr John Smith in the Virgin New Adventures novel Human Nature, or that his origins have become muddied by agents manipulating his personal timestream (the Eighth Doctor Adventures novel Unnatural History). In the New Series Adventures novel The Deviant Strain by Justin Richards, the Doctor comments that his DNA is "close" to that of humans. However, as noted above, the canonicity of the novels is uncertain.

When incarnations meet

Due to time travel, it is possible for the Doctor's various incarnations to encounter and interact with each other, although this is supposed to be prohibited by the First Law of Time (as stated in The Three Doctors), or only in the "gravest of emergencies" (The Five Doctors). In the television series, such encounters have been seen on three occasions, in The Three Doctors (1973), The Five Doctors (1983) and The Two Doctors (1985). In Day of the Daleks (1972), the Third Doctor and Jo Grant very briefly met their future selves due to a glitch during a temporal experiment. In Father's Day (2005), the Ninth Doctor and Rose observed but did not interact with past versions of themselves; when Rose changed history, the earlier selves vanished and a temporal paradox was created that attracted the extradimensional Reapers.

Physical contact between two versions of the same person can lead to an energy discharge that shorts out the "time differential". This is apparently due to a principle known as the Blinovitch Limitation Effect, and was seen when the past and future versions of Brigadier Lethbridge-Stewart touched hands in Mawdryn Undead. Oddly, the Doctor's incarnations do not appear to suffer this effect when encountering each other and shaking hands. Why this is has never been explained; fan theories include the possibility that this may have something to do with regeneration rendering the different incarnations effectively different people. An essay in the About Time series by Lawrence Miles and Tat Wood suggests that Time Lords are somehow exempt from the effect by their very nature. Rose Tyler is seen holding an infant version of herself in Father's Day, with no visible energy discharge, but the contact does allow the Reapers to enter the church.

The interaction of the Doctor's various incarnations produces a continuity anomaly that requires suspension of disbelief on the part of viewers, as one may assume that his past selves would forget that he would later regenerate. In Castrovalva, the newly-regenerated Fifth Doctor clearly indicates that the outcome of his regeneration can not be predicted; however, the Fifth Doctor should have had memories from his earlier incarnations of having met himself per the events of The Three Doctors and The Five Doctors. Also, the Second, Third and Fifth Doctors should be already familiar with the events of The Five Doctors, having already lived through them multiple times. It has been suggested in fanon that the Time Lords erase the Doctor's memory after such encounters. The Virgin Missing Adventures novel Cold Fusion by Lance Parkin suggests it is sometimes, but not always, due to something called "Blinovitch Conservation".

Reprising the role

On a few occasions, previous Doctors have returned to the role, guest-starring with the incumbent:

• William Hartnell and Patrick Troughton with Jon Pertwee in The Three Doctors. Originally Hartnell's role had been intended to be more extensive, but his health had deteriorated to the extent that he could only make a limited appearance. In the end, it turned out to be his last television role.
• Troughton, Pertwee with Davison in The Five Doctors, the twentieth anniversary special, with another actor, Richard Hurndall, standing in for the late William Hartnell. The story began with a clip featuring Hartnell. Tom Baker declined to appear, feeling that the role came too soon after he had left the programme (a decision he later said he regretted) and the narrative was reworked to use clips from Shada, an intended six-part story from the Fourth Doctor's era that was never completed due to industrial action. A waxwork dummy of Baker was used in the publicity photographs.
• Patrick Troughton with Colin Baker in The Two Doctors.
• Jon Pertwee, Tom Baker, Colin Baker, Peter Davison and Sylvester McCoy — with rubber dummy heads standing in for William Hartnell and Patrick Troughton — in Dimensions in Time, a charity special in aid of Children in Need in 1993, the programme's 30th anniversary year. Except for the mannequin versions of Hartnell and Troughton, no two Doctors are shown on screen at the same time.
• Sylvester McCoy in the 1996 television movie, to hand over the role to Paul McGann.

Other actors have portrayed the character of the Doctor outside of the television series. For details on this see under Adaptations and other appearances in the main article and Doctor Who spin-offs.

For a list of all actors who have played the Doctor see List of actors who have played the Doctor.

The Doctor's age

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The Doctor's age has been stated (or estimated) in several stories. In the serial The Tomb of the Cybermen, the Second Doctor told Victoria that he was around 450 years old. The Second Doctor was also seen to carry around a 500-year diary in which he kept notes. The Third Doctor implied that he had a lifetime that covered several thousand years, but he may have been referring to the time span he had seen on his travels rather than actually lived through, or perhaps his own life expectancy.

By the time of The Brain of Morbius, the Fourth Doctor was stated to be 749 years old ("something like 750 years" in the prior Pyramids of Mars). In The Ribos Operation, the first Romana said the Doctor was 759 years old and had been piloting the TARDIS for 523 years, making him 236 when he first "borrowed" it. In Revelation of the Daleks the Sixth Doctor was 900 years old, and in Time and the Rani, the Seventh Doctor's age was the same as the Rani's, namely 953. In Remembrance of the Daleks the Seventh Doctor said that he had "900 years’ experience" rewiring alien equipment. At the beginning of the 1996 television movie, the Seventh Doctor was seen to have a 900-year diary in his TARDIS.

The large gap in years between the Fourth and Sixth Doctors can be partially covered by the fact that the Fourth Doctor travelled alone for a time or with an equally long-lived Time Lady as a companion, allowing for several decades or centuries of untelevised stories to take place. Such gaps occur between the stories The Deadly Assassin and The Face of Evil when he travelled without a companion and between The Invasion of Time and The Ribos Operation when he was accompanied by K-9. Another potential gap occurs between The Horns of Nimon and The Leisure Hive when he travelled with Romana. The Face of Evil also revealed that the Fourth Doctor travelled on his own at a point prior to that serial (the chronology of this is not revealed in the story, but the novelisation places it within the events of Robot, right after his regeneration).

While the Fifth Doctor was never seen without a companion, there was a period (between Time-Flight and Arc of Infinity) where he was travelling with Nyssa of Traken, who, not being human, may not have aged normally. There was also a gap just after The Trial of a Time Lord which can account for the difference in ages between the Sixth Doctor in Revelation of the Daleks and the Seventh Doctor in Time and the Rani. Likewise, the gap between the Second and Fourth Doctors is occasionally explained as part of the "Season 6B" theory. One other possible gap occurs between Seasons 10 and 11, when the Third Doctor was between companions and could have spent time adventuring on his own before returning to Earth, and UNIT.

In the spin-off novels, the Seventh Doctor celebrated his 1000th birthday in Set Piece by Kate Orman, and the Eighth Doctor declared his age to be 1,012 in Vampire Science by Orman and Jonathan Blum. The Eighth Doctor also spent nearly a century on Earth during a story arc spread over several novels.

In the 2005 series, the Doctor's age is stated in publicity materials as 900 years, and in Aliens of London, he says, "Nine hundred years of time and space, and I've never been slapped by someone's mother." Rose follows up by asking him if he is 900 years old, and he replies affirmatively. He restates his age as 900 in The Doctor Dances.

How this figure is to be reconciled with the Doctor's age in the rest of the series and other (arguably non-canon) sources is uncertain. Possibilities include the Doctor estimating his age (900 years being "how old" he is, generally speaking, rather than his specific age) or lying about it out of vanity (in The Ribos Operation he gave his age at 756, although Romana insisted it was 759).

Another possibility is that the Doctor is simply referring to the years he has been travelling for simplicity's sake, as opposed to his physical age. In The Empty Child he speaks of 900 years of "phone box" travel, which, if he began at 236, would make him 1,136 years old. This figure does fit roughly with the Eighth Doctor's period as chronicled in the spin-off media (including his century-long exile on Earth). In fact, considering that the TARDIS did not acquire its police box shape until it landed in London prior to "An Unearthly Child", he may be even older. Of course, all this also presupposes that the figures given correspond to Earth years and not Gallifreyan.

The Doctor and romance

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As the Doctor had a granddaughter, it was implicit from the beginning that he probably had had, at some point, romantic or at least sexual relations with someone (in Fear Her (2006), he states that he was once a father). However, Hartnell's age precluded any involvement of the character with the only other female lead at the time. The First Doctor did flirt with — and was accidentally engaged to — the character Cameca in The Aztecs; although this was part of a ploy to get the TARDIS back, there was a hint of mutual attraction in Hartnell's performance (especially as he is ultimately unable to leave behind the love token she has given him). The fact that the TARDIS crew kept pressing forward in their travels was probably also a factor in preventing any romantic attachments.

As the series progressed and grew more popular among children, the Doctor was firmly established as an avuncular figure to his younger companions, the one exception being the Third Doctor's hurt reaction to his companion Jo Grant's leaving him for an idealistic scientific adventurer whom she describes as "a younger version" of the Doctor (The Green Death).

Despite the press (and, occasionally, the production team) trying to play up the sexiness of some of the female companions or suggesting "hanky panky" in the TARDIS, the series reached the point where any suggestion of the Doctor as a sexual being was avoided altogether. One example was during City of Death, when the Fourth Doctor says to Countess Scarlioni, "You're a beautiful woman, probably," implying that he is incapable of appreciating a human woman's attractiveness. This rule held true even when the Doctor's apparent age was closer to those of his companions, or if there was on-screen chemistry between the actors (as there was between Fourth Doctor Tom Baker and his wife-to-be Lalla Ward's Romana II).

The perception of the Doctor as an essentially sexless character, uninterested in romance, is why some portions of fandom reacted so strongly to the Eighth Doctor (Paul McGann) kissing Dr. Grace Holloway in the 1996 television movie, breaking the series' long-standing taboo against the Doctor having any romantic involvement with his companions (also see here). By contrast, for example, Peter Davison is on record as saying that during his era (Fifth Doctor) he was instructed to avoid putting even a fatherly arm round any but his male companions. (Though in Kinda, he and older guest star Nerys Hughes do offer a subtle suggestion of attraction between their characters.)

However, the spin-off media both before and after the television movie have toyed with the idea in various ways. In the 1995 Virgin New Adventures novel Human Nature by Paul Cornell, the Seventh Doctor takes on the human guise of "Dr John Smith" and has a romance with a history teacher in 1914, albeit as a means to understand the human condition and with the Doctor's own memories as a Time Lord suppressed. In various novels — especially Lungbarrow — it is also established that Time Lords do not reproduce sexually, but emerge from genetic Looms fully grown, although in equivocal fashion the same book also hints that the Doctor's birth was an exception. Madame de Pompadour's reference to the Doctor's lonely childhood in The Girl in the Fireplace would also seem to contradict the Loom theory. The classic series also made occasional references to the Doctor's childhood on Gallifrey (The Time Monster, State of Decay and Black Orchid) and there had been the odd reference to Gallifreyan children.

In the Big Finish Productions audio play Loups-Garoux, the Fifth Doctor reluctantly agrees to marry the werewolf Ileana De Santos and although he gets out of it later there is, as in Cameca's case, a degree of mutual attraction present. In the plays involving the Eighth Doctor, his companion Charley confesses her romantic feelings for him (in Zagreus), but although he admits he loves her back at the time, it is a highly dramatic moment and the relationship does not progress beyond the platonic.

The 2005 series played with the idea of a romantic relationship between the Ninth Doctor and Rose Tyler, with many characters assuming they were a couple (although they always both denied it), and Rose's boyfriend Mickey Smith clearly viewing the Doctor as a romantic rival for whom Rose has, in some sense at least, left him. Both also showed flashes of jealousy when the other flirted with other characters. In the episode The Doctor Dances, in which writer Steven Moffat used dancing as a metaphor for sex, Rose said Harkness was like the Doctor, "only with dating and dancing." The Doctor responded testily, "I'm 900 years old. I think you can assume that at some point I've... danced." In the finalé for that season, The Parting of the Ways, the Doctor even kissed Rose (although the kiss also served a plot purpose). Earlier in the same episode, the bisexual Jack kissed both the Doctor and Rose goodbye full on the mouths before leaving to fight the Daleks.

In the New Series Adventures novel Only Human by Gareth Roberts, Rose asks the Doctor how he would know that marrying for love is overrated, to which he cryptically answers, "Who says I don't? You ask the Lady Mary Wortley Montagu." In a December 2005 interview on BBC 4, actor David Tennant described the relationship between the Doctor and Rose as "basically a love story without the shagging", and indicated that the romantic elements would continue in the 2006 series; he also suggested that the Doctor's sexuality would be "gently explored".

In the 2006 series, the Doctor and Rose kiss in New Earth, but Rose is possessed by Cassandra at the time. In School Reunion, the arrival of the Doctor's previous companion, Sarah Jane Smith, and his reaction to seeing her again prompts jealousy and worry from Rose, and Sarah all but admits that she has long been in love with the Doctor. In the same episode, the Doctor also hints at deeper feelings for his companions when he remarks that humans wither and die, and it is hard to watch that "happen to someone you..." but leaves the rest unsaid. In the following episode, The Girl in the Fireplace (also written by Steven Moffat), the Doctor shares a passionate kiss and a strong romantic connection with Madame de Pompadour, who takes him away to "dance", but how far the metaphor is taken is not seen on screen.

In The Impossible Planet the Doctor and Rose share an awkward moment when they have to consider settling down in one time period and Rose suggests they do so together. In The Satan Pit he tells Ida Scott that Rose already knows how he feels about her. In Doomsday, when the Doctor says his goodbyes to Rose, she tells him that she loves him. He begins to reply, but only gets as far as saying her name before he gets cut off, and the next scene shows him crying alone.

Discontinuities

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A common contention among fans and producers of the series is that a large part of the Doctor's appeal comes from his mysterious and alien origins. While over the decades several revelations have been made about his background — that he is a Time Lord, that he is from Gallifrey, among others — the writers have often strived to retain some sense of mystery and to preserve the eternal question, "Doctor who?" This backstory was not rigidly planned from the beginning, but developed gradually (and somewhat haphazardly) over the years, the result of the work of many writers and producers.

Understandably, this has led to continuity problems. Characters such as the Meddling Monk were retroactively classified as Time Lords, early histories of races such as the Daleks were rewritten, and so on. The creation of a detailed backstory has also led to the criticism that too much being known about the Doctor limits both creative possibilities and the sense of mystery.

Some of the stories during the Seventh Doctor's tenure, part of the so-called "Cartmel Masterplan", were intended to deal with this issue by suggesting that much of what was believed about the Doctor was wrong and that he was a far more powerful and mysterious figure than previously thought. In both an untelevised scene in Remembrance of the Daleks and the subsequent Silver Nemesis it was implied that the Doctor was more than "just another Time Lord." The suspension of the series in 1989 meant that none of these hints were ever resolved. The "Masterplan" was used as a guide for the Virgin New Adventures series of novels featuring the Seventh Doctor, and the revelations about the Doctor's origins were written into the novel Lungbarrow by Marc Platt. However, the canonicity of these novels, like all Doctor Who spin-offs, is unclear.

While some fans regard discontinuities as a problem, others regard it as a source of interest or humour (an attitude taken in the book The Discontinuity Guide). A common fan explanation is that a universe with time travellers is likely to have many historical inconsistencies. There has also been much fan speculation centred on exactly which aspects of the television series, books, radio dramatisations, and other sources were considered canon in the 2005 series.

Other appearances

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• In the comic Death's Head
• In various episodes of The Simpsons including Treehouse of Horror X (see Doctor Who spoofs)
• With Dan Dare in the 1991 Comic Relief Charity Magazine.^*

Footnotes

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References

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External links

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• Who's Doctor Who — biography based on the TV series only
• The Doctor's Biography — biography based on the TV series plus other media
• Marvel Appendix: Doctor Who entry

Doctor Who Doctors