Of particular note to Star Trek fans is Jeffrey Combs (of Re-Animator fame), who made his Star Trek debut on Deep Space Nine. Combs has stated that he had auditioned for the role of William T. Riker on Next Generation, but when Jonathan Frakes (who won the part) later directed the DS9 episode "Meridian", he recommended Combs for a part.This comes from an interview dated January 30, 2003, which can be found on the fifth season DVD set of Deep Space Nine as a "Hidden File". Combs would go on to appear in thirty-one episodes of Deep Space Nine, playing four distinct characters—five if one counts the "mirror universe" version of Brunt as a distinct character. In "The Dogs of War", he also became the only Star Trek actor to play two distinct roles (those of Brunt and Weyoun) in a single episode.

Morn, a minor character who frequents Quark's bar, is the only named character in the series who never utters a single line of dialogue. So great was the fan support for the silent character that a special episode called "Who Mourns for Morn?" was written for him in the sixth season. Morn’s name is an anagram of the character Norm from Cheers, who also spent seemingly all of his time sitting on his favorite bar stool and drinking. Ironically, for a character who never spoke, the other characters commented on what an extremely talkative person he was.

Several of the series’ prominent recurring characters are also known for their work on other projects, the most prominent of whom were Academy Award winner Louise Fletcher (the Bajoran spiritual leader Kai Winn) and sci-fi veteran Salome Jens (the Female Changeling). Other prominent celebrities seen in guest and recurring roles included Vanessa L. Williams, Wallace Shawn, Lark Voorhies, James Cromwell, Gabrielle Union, Iggy Pop, Steven Berkoff and James Darren. John Colicos reprised his TOS role as Kor on several occasions.

Plots

Deep Space Nine also differs from previous Star Trek series in that it contains more story arcs that span several episodes and, indeed, seasons. Previous Star Trek series tend to restore the status quo ante at the end of an episode so that the episodes could be seen out-of-order without compromising their plots. On Deep Space Nine, however, not only are events in one episode often referenced and built upon in later episodes, but sometimes several episodes in a row are cliffhangers. This trend is especially strong near the end of the series’ run, by which point the show is very much a serial, and it was very much intentional, as the producers have all stated that they felt it enriched the show.

One such story arc is Benjamin Sisko’s role as a religious icon. He initially faces it with open discomfort and skepticism, referring to the Bajoran Prophets simply as "wormhole aliens" and striving to keep his role as commander of the station distinct from any obligations that the Bajorans try to place on him. Later, he becomes more accepting of his role and, by the end of the series, he appears to openly embrace it.

The station crew early on contend with a terrorist group known as the MaquisMore than likely, the Maquis were named for the French resistance group of the same name that fought against Nazi Germany in World War II.. Rooted in the events of The Next Generation episode "Journey's End", in which a group of Native American settlers refuse to leave when their colony world is given to Cardassia as part of a treaty, the Maquis are an example for the show’s exploration of darker themes: Its members are Federation citizens who take up arms against Cardassia in defense of their homes, and some—such as Calvin Hudson, a long-time friend of Sisko's, and Michael Eddington, who defects while serving aboard the station—are former Starfleet officers. The show’s violent departure from traditional Star Trek themes can be seen in episodes such as "For the Cause", in which Eddington tells Sisko, "Everybody should want to be in the Federation. Nobody leaves paradise. In some ways you’re even worse than the Borg. At least they tell you about their plans for assimilation. You assimilate people and they don’t even know it."

The second-season episode "Rules of Acquisition" introduces the Dominion, a ruthless empire in the Gamma Quadrant. It is led by "the Founders", a race of shapeshifters known as Changelings—the same race as station security chief Odo. They were once persecuted by non-shapeshifters (whom they call "Solids") and they seek to instill "order" upon those who might otherwise cause them harm—including the Solids. The Founders have created two races to serve them: the Vorta, sly and subversive diplomats, and the Jem’Hadar, their vicious shock troops. These races worship the Founders as gods.

The Dominion forms an uneasy alliance with the Cardassians in the fifth-season episodes "In Purgatory's Shadow" and "By Inferno's Light" and goes to war with the other major powers of the Alpha Quadrant. Throughout the series, loyalties and alliances change repeatedly: alliances with the Cardassians are made, broken, and remade; a short war with the Klingons flares and settles, and the Federation finds an alliance with the Romulans.

Another example of DS9’s darker plot material is Section 31, a secret organization that exists within the Federation, dedicated to preserving the Federation way of life at any and all cost. This undemocratic shadow organization, introduced in "Inquisition", justifies its unlawful and ethically questionable tactics by claiming that it is essential to the continued existence of the Federation. Section 31 features prominently in several episodes of the Dominion War arc; such darker plot elements, as well as DS9’s relative lack of exposure compared to its predecessor, garnered the show a reputation as the "black sheep" of the Trek family.The Pittsburgh Post-Gazette used this phrase in a November 30, 1999 editorial (which can be found archived on Brannon Braga’s official website), as did Exclaim! magazine in a March 31, 2003 review. (Despite the connotations associated with the phrase "black sheep", however, the writers of both articles spoke highly of the series.)

At the start of Deep Space 9’s third season ("The Search"), with the threat of a Dominion attack looming on the other side of the wormhole, Commander Sisko returns from a trip to Starfleet Headquarters on Earth with the USS Defiant, a prototype starship that was built to fight the Borg, but is determined to be 'overgunned and overpowered'. It remains stationed at Deep Space Nine until the end of the series, providing not only defense but also an avenue by which plotlines could progress without being limited by the stationary nature of DS9 itself.

Many fans believe that the Dominion War was the height of DS9 and, according to Michael Piller, tend to overlook the first two "pre-Dominion" seasons. However, Piller has indicated that the second season was his favorite.

In DS9, the Ferengi are no longer an enemy of the Federation, but rather an economic power whose political neutrality is, for the most part, respected. Several episodes explore the capitalist nature of the Ferengi, while others delved into the race’s sexist social norms. Ferengi are guided in their lives and in their business transactions by the Rules of Acquisition.

Interpersonal conflict between regular characters was something previously forbidden by Roddenberry in The Original Series and The Next Generation, but features prominently on DS9. This was brought about at the suggestion of The Next Generation’s writers (many of whom also wrote for DS9) because they felt that the prohibition on interpersonal conflict between the main characters limited their ability to develop new and interesting stories. The intentional coming together of different people whose values and agenda regularly conflicted with one another was intended to bring a new dimension to the series; in Piller's words, "people who come from different places—honorable, noble people—will naturally have conflicts".

Several of the characters also have their own personal demons and stories that are rather specific to their character. For instance, Jadzia Dax, a Trill, has seven lifetimes' worth of memories as a result of her joining with the Dax symbiont. Security chief Odo, a Changeling, yearns to find others like him and believes he is the only one of his kind; later, he finds his own people are the ruthless leaders of the Dominion and is torn between his desire to join them, his sense of morality, and his love for Kira Nerys. Meanwhile, Worf struggles (even more so than on The Next Generation) with conflicting loyalties to the Federation and his own people, the Klingons – as well as life on the station, which he finds is not at all what he expected.

Themes

The most prominent theme in the series is that of the deeply religious Bajoran people attempting to rebuild their world and their economy after sixty years of oppression from Cardassia. The relationship between the Bajorans and the Cardassians is intentionally portrayed as a powerful Holocaust allegory, though there are also striking comparisons to be made with the Serbian occupation of Bosnia, the Japanese occupation of Korea, the Israeli-Palestinian conflict, or the Armenian Genocide. The Cardassians had put the Bajorans to work in forced slave labor camps under terrible conditions, killed them with impunity, and now refuse to acknowledge the atrocities that occurred during the Occupation, as depicted in "Duet", "Things Past", etc. Deep Space Nine’s first officer, Kira Nerys, who was formerly an underground resistance leader responsible for many acts of sabotage and subversion aimed at the Cardassians, is required in her new role as Bajoran Liaison Officer and the station’s First Officer to learn diplomacy and patience.

The relationship between the Cardassians and the Bajorans could also be regarded as colonial in nature. Much like Kipling’s "The White Man's Burden", the Cardassians believed themselves both technologically and culturally superior to the Bajorans they had subjugated. According to Dukat ("Waltz"), at the time of first contact, Cardassia was at least a century ahead of Bajor "in every way". The Cardassians strip-mined Bajor and instituted forced labor camps under the guise of civilizing a lesser people. Guerrilla tactics by Bajoran fighters led to their freedom in the same way that many colonies gained their independence in the 1960s and 1970s.

The Star Trek universe portrayed in Deep Space Nine is one of power politics among the galaxy’s great powers. Prior to the series, the Federation was depicted as a near utopian society guided by human rights, or rather, sentient rights. In contrast, the Federation in Deep Space Nine tries to balance its high ideals with the practical realities of galactic politics. Kira Nerys, in the pilot episode, says 'We finally drive the Cardassians out, and what do our new leaders do? They call up the Federation and invite them right in!'

Another theme DS9 visited on several occasions is the idea that the universe is not perfect and there is often no right or wrong answer to difficult situations. This theme is embodied by the Maquis storyline; members of the Maquis were neither enemies nor criminals; they take up arms against Cardassia in defense of their homes. Perhaps a quote from Sisko in the second-season episode "The Maquis, Part II" best describes not only the Maquis but also the stark contrast between DS9 and its predecessors:

"On Earth there’s no poverty, no crime, no war. You look out the window of Starfleet headquarters and you see... paradise. Well, it’s easy to be a saint in paradise. But the Maquis do not live in paradise. Out there in the Demilitarized Zone, all the problems haven't been solved yet. Out there, there are no saints... just people. Angry, scared, determined people who are going to do whatever it takes to survive. Whether it meets with Federation approval or not."

Awards and distinctions

"Think of it. Five years ago no one had ever heard of Bajor or Deep Space Nine. Now all our hopes rest here. Where the tides of fortune take us, no one can know." - Gowron, voicing Rick Berman and Brannon Braga's thoughts in "By Inferno's Light"

Critically, the show has received much acclaim for its character and plot development. Even minor characters tended to be multi-faceted; for instance, StarTrek.com in an article about Star Trek's greatest villains described Gul Dukat as "possibly the most complex and fully-developed bad guy in Star Trek history"Source: http://www.startrek.com/startrek/view/features/specials/article/1617.html. Dukat in particular was the focus of several episodes, such as the sixth-season episode "Waltz", in which he has gone insane and begins to hallucinate, and "Covenant", in which he becomes a twisted messianic figurehead for a group of Pah Wraith-worshipping Bajorans.

The series was not without its detractors , but ultimately Michelle Erica Green, reviewer for the fan site Star Trek Nation, said in her review of the series finale "What You Leave Behind": "This is a grand, satisfying conclusion to this greatest of Star Trek series."

Criticism