In one episode, while Kira is still pregnant the O'Briens' baby, she screams at Dr. Bashir (Alexander Siddig) "This is all your fault!" This is an in-joke referring to the fact that actress Nana Visitor and Siddig were expecting a child in real-life.
Although all Star Trek series dealt with complex social issues, Deep Space Nine had darker undertones and seriously dealt with genocide, terrorism, bigotry, racism, shell shock and the consequences of war much more than other Star Trek series.
The Dominion storyline was originally only meant to span two episodes. Ronald D. Moore and Ira Steven Behr lobbied to make the storyline ongoing, but met with resistance from Executive Producer Rick Berman who wanted to maintain an episodic format to the series. After Berman left production to oversee the launch of 'Star Trek: Voyager (1996)', Moore and Behr were given more creative control over this series, making the Dominion War the main plot of the show and adopting a serialized format.
According to an April 2003 interview, Avery Brooks was initially required by contract to appear with hair in order to prevent confusion with his Spenser: For Hire (1985) character, Hawk. In later seasons, as Sisko became established, Brooks was allowed to shave his head and re-grow his beard.
The primary design of Deep Space Nine is based off a gyroscope, but with the top and bottom parts removed. Some of the earlier designs of DS9 by Herman F. Zimmerman had complete hoops, also like a gyroscope, and the idea was that rotating the station would create artificial gravity, until someone pointed out that there was no need for this, as Star Trek ships use gravity generators. However, the idea of a halo-shaped space station stuck, and it was used in the final design.
This is the only "Star Trek" TV series not to have any human female as part of the main cast. Kasidy Yates is the only human female recurring character, too. This doesn't mean anti-feminism, as alien females (and Kasidy too) shows often strong and determined (if not stronger, like Kira) as their male counterparts.
Dax was originally envisioned as an alien from a low-gravity world forced to get around in a wheelchair and who flew around her quarters; the concept was scrapped and recycled into the character of Melora because the "flight" cables were too difficult to rig.
The name Deep Space Nine originated from an early working title, and predated the decision to set the series on a space station. Producers intended on coming up with a new title after the show was fully developed, but stayed with the Deep Space Nine name feeling it had an intriguing quality to it.
Malcolm McDowell once said he'd like to appear on DS9, but only if his nephew - Alexander Siddig (who plays DS9's Dr. Bashir) - would direct the episode. Unfortunately, this never panned out, mostly due to scheduling conflicts.
Executive Producer/Co-Creator Michael Piller said that when coming up for an idea for the series concept of Star Trek: Deep Space Nine (1993), there were initially three ideas toted around: Another starship adventure, a space station concept, and a remote frontier colony. The frontier colony idea was briefly considered, with the idea that since Star Trek (1966) was compared to Captain Horatio Hornblower R.N. (1951) in outer space, the new series would be compared to Gunsmoke (1955), but on a remote planet. The frontier colony idea was eventually dropped since it would've required a lot of on-location shooting, and the space station idea was ultimately developed instead.
The character that eventually became Vic Fontaine was written for Frank Sinatra Jr.. in Season 4. Sinatra, despite being a fan of the show, turned it down, declaring that he only wanted to play an alien. After meeting with Robert Goulet, and attempting to get Steve Lawrence, Tom Jones and Jerry Vale, the producers eventually decided on James Darren in Season 6. Darren would go on to appear in 8 episodes, including the series finale.
After production ended and the sets were dismantled, the Defiant bridge set was declared "fold & hold" and placed in storage. It has been redressed and reused as the bridge of an alien cargo ship and a Klingon battlecruiser on Star Trek: Voyager (1995) and the bridge of the ECS Fortunate on Star Trek: Enterprise (2001).
The number 47 pops up an inordinate amount of times on computer screens, serial numbers, dates and so on. This tradition was started by writer/co-producer Joe Menosky and was soon picked up by the rest of the production team. Menosky said that he choose that particular number because when he was a college student at Pomona College, Professor of Mathematics Donald Bentley proved as a joke that all numbers are equal to 47. Interestingly, the later series Alias (2001) also featured the number 47 many times, and incorporated it into its ongoing storyline.
The uniforms initially worn on DS9 were designed to look different from those worn on its parent show, Star Trek: The Next Generation (1987) Beginning with the movie Star Trek: Generations (1994), however, these new uniforms were adopted by the TNG crew and Starfleet as a whole. From the mid-5th season of DS9 and Star Trek: First Contact (1996) another type of uniforms were issued by Starfleet, while Star Trek: Voyager (1995) (having no way of knowing about the change) retained the earlier version, distinguishing the two series from each other again. It is also worth mentioning that the DS9-style uniforms are very similar to the ones worn by Starfleet cadets in TNG, most notably in Star Trek: The Next Generation: The First Duty (1992).
Although we only rarely see it, there is an ATM in Quark's bar. It dispenses the various types of currency used by major races visiting the station: Federation credits, Bajoran litas, Cardassian leks, and Ferengi latinum.
The character Elim Garak is a former spy who works as a tailor on the station. In many of 'John Le Carré''s spy novels a tailor is one of the main characters (and is often also acting as a spy). "The Tailor of Panama" and "Tinker, Tailor, Soldier, Spy" are two examples.
Benjamin Sisko is the only Captain in a Star Trek series that didn't start out as a Captain at the beginning of the series. From Seasons 1-3, Sisko held the rank of Commander. It wasn't until the Season 3 finale, Star Trek: Deep Space Nine: The Adversary (1995), where he was finally promoted to Captain.
Aron Eisenberg was approaching his mid 20s when cast as Nog, who began on the series in his pre to early teens. In addition, Eisenberg was only 17 years younger than Max Grodénchik who played Nog's father Rom.
Terry Farrell left the series after the sixth season to co-star on the Ted Danson sitcom Becker. It is unclear as to why Farrell opted for the series over renewing her contract for DS9's final season. Farrell did saw she was open to returning for an episode if a way was found to temporarily resurrect Jadzia Dax in some way (i.e. Ghost/Spirit. Duplicate/Clone, Alternate Universe Counterpart, etc)
In the episode Trials and Tribble-ations, Crew from Deep Space Nine are hijacked into the episode Trouble with Tribbles from Star Trek (1966). The set of the original Enterprise was re-created for this episode in detail except for the orange grating often seen in engineering areas. Apparently, the company that made it had discontinued its production.
References are frequently made to Starfleet "ground troops," and some Starfleet characters have different uniforms (a black uniform with a small colored stripe across the middle). Fans generally accept that these characters are part of a Starfleet Marine Corps, although this has never been explicitly stated on-screen. There was a Starfleet Colonel West in Star Trek VI: The Undiscovered Country (1991); West was most likely a Starfleet Marine, since navies do not have the rank of colonel. Colonel West was played by Rene Auberjonois, who plays Constable Odo on Star Trek: Deep Space Nine (1993).
The appearance of the Trill symbiont is different from when it initially appeared on the episode Star Trek: The Next Generation: The Host (1991). In that episode, the symbiont's appearance was made to resemble a caterpillar with the head of an octopus. According to Make-Up Supervisor Michael Westmore, the symbiont was re-made for this series to be more "stream-lined" to make it easier to handle. Also, the appearance of the Trill hosts had changed as well. In "The Host", the Trill people had semi-ridged foreheads and no body spots, but in this series, they have normal foreheads, and body spots. In "The Host," the Trill was also terrified of being transported, insinuating that it would damage the symbiont, but neither Jadzia nor Ezri ever mentioned concerns with being transported.
Terry Farrell was the only regular Star Trek actor or actress not to return in any way after their character was killed off. Leonard Nimoy's Spock was resurrected, and Denise Crosby made appearances as an alternate universe counterpart to and later daughter of Tasha Yar.
Both Armin Shimerman (Quark) and Marc Alaimo (Gul Dukat) have appeared as one of the first actors to portray members of their respected species, and both appeared on Star Trek: The Next Generation (1987). Shimerman played the the Ferengi officer Letek on the TNG episode "The Last Outpost" (#1.04), while Alaimo played the Cardassian officer Gul Macet on the TNG episode "The Wounded" (#4.17).
The design of Ops incorporates ideas that were considered but dropped for The Bridge on Star Trek: The Next Generation (1987), such as the upper level office, the briefing table in the center of the room, and the transporter being built into the set.
On occasion, sets from Star Trek: Voyager (1995) are used as other Starfleet locales. (For example: a holosuite grid in the episode "Inquisition", the entire U.S.S. Bellerophon [which was an Intrepid-class starship just as Voyager is] in the episode "Inter Arma Enim Silent Leges.")
Worf and Jadzia Dax were the first pair of regular Star Trek characters to be married to each other. Tom Paris and B'Elanna Torres eventually got married on Star Trek: Voyager (1995), and later Riker married Troi in _"Star Trek: Nemesis" (2002)_. O'Brien was only a recurring character at the time of his marriage on Star Trek: The Next Generation (1987), and his wife Keiko was not a regular character on either TNG or DS9.
One of the original ideas of the station was based on the biblical Tower of Babel, meaning that it had been created over as long as 3000 years, through the cooperation of many different alien races who could not effectively communicate with one another, using different technologies that were often incompatible with each other. It was finally decided that the space station would be Cardassian in design, with lots of circular design elements.
Marc Alaimo has a naturally long neck, and the Cardassian neck ridges were thought of based on this. They enhanced his long neck and it looked great on him. When Alaimo was on the set for an episode, the rest of the cast and crew even referred to him as "The Neck".
Military ranks used in Star Trek are all based upon actual military ranks. Starfleet ranks are those of the US Navy: Ensign, Lieutenant Junior Grade, Lieutenant, Lieutenant Commander, Commander, Captain, Rear Admiral, Vice Admiral, and Admiral. Bajoran ranks are the same as those used in the US Army, Air Force, and Marines: 2nd lieutenant, 1st lieutenant, Captain, Major, Lieutenant Colonel (or, as the Bajorans call it, 'Field Colonel'), Colonel, and General. (Kira, after her promotion, was referred to simply as 'Colonel', but she was promoted two steps in rank at once.) Klingon ranks are 'bekk' (an enlisted rating), Ensign, Lieutenant, Commander, Captain, Colonel, Brigadier, General, Admiral. Cardassian ranks are based on those of the ancient Roman Empire: Gil (equivalent to a Starfleet/ US Naval Lieutenant), Glinn (Commander), Gul (Captain), and Legate (Admiral).
Buck Bokai's baseball card, a collectable featured on Benjamin Sisko's desk, had actor Keone Young on the front, in character, but showed "Trek" model maker Gregory Jein, who invented the "history" of the character, on the back. The pair bore an uncanny resemblance to each other.
In the episode "By Inferno's Light", several of the main characters are imprisoned in a Dominion POW camp. One of the characters, Elim Garak, must overcome his fear of claustrophobia to try and get them out. This has a lot of comparison with Charles Bronson's character in The Great Escape (1963).
O'Brien was the first regular Star Trek character to be established as being married from the start of a Trek series. (He had gotten married on the Star Trek: The Next Generation episode Star Trek: The Next Generation: Data's Day (1991) as a recurring character on the show). In addition, Sisko was the first Star Trek Captain to be permanently married when he wed Kassidy Yates.
The show featured the largest cast of recurring or semi-regular characters of any Star Trek TV series. That's mostly due because Deep Space 9 is a huge space station (orbiting around planet Bajor) opened to be visited, while in the other shows they are very smaller traveling spaceships.
Producers noted virtually no negative reaction to the romantic pairing and eventual wedding between Worf and Dax, which was essentially interracial. Producers cited that on the generally open minded nature of the Star Trek fan base. As was the case with all other Star Trek programs, the series depicted a number of mixed race romances, notably married couples O'Brien and Keiko, and Rom and Leeta.
Buck Bokai, a baseball player of the 21st Century, broke Joe DiMaggio's record for consecutive hits in 2026. While the name is never mentioned, this fact is mentioned in the Star Trek: The Next Generation (1987) episode "The Big Goodbye."
The Dominion War storyline proved very divisive among veterans of the "Star Trek" universe. George Takei, in particular, voiced his belief that the storyline was directly antithetical to Gene Roddenberry's original concept of a peaceful, Utopian future.
The character of Morn, the Lurian bar patron whom is seen always sitting at Quark's bar, was written as a nod to the character Norm Peterson, played by George Wendt in the long-running American sitcom "Cheers", Morn is an anagram of Norm. Terry Farrell left DS9 to star opposite Ted Danson in "Becker". Ted Danson played Sam Malone in "Cheers".
Before she was Jadzia Dax, Terry Farrell played The Cat in the 2nd pilot of the American version of the long-running British science fiction sitcom "Red Dwarf". Patrick Stewart, (Captain Jean-Luc Picard in "Star Trek: The Next Generation") is a fan of "Red Dwarf".