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 (1995), 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.
Jadzia Dax was originally supposed to have a forehead appliance as the Trill were first shown in Star Trek: The Next Generation: The Host (1991), but after a test, most people thought that Terry Farrell's face was much too beautiful to be partially covered by/with prosthetics. Instead, she got to have spots on the side. They were drawn on personally by Michael Westmore each day, a process which took over an hour. Westmore actually 'signed' his work by adding two spots in the shape of an M and a W. From then on, all Trills were shown to be like this rather than the version shown on Star Trek: The Next Generation, and the difference between the two was never explained.
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.
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 writers also found that due to the static environment of a space station, it was much easier to have the characters deal with the long-term consequences of their actions, as opposed to a starship crew, who would be in different locations each week.
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.
There was a level of friction between fans of Babylon 5 (1994) and Star Trek: Deep Space Nine. Babylon 5 fans felt that writers for Deep Space Nine had stolen many aspects of Babylon 5's premise (occurring recently after a war/occupation, episodes taking place on a space station not located in Earth territory, the cast discovering an ancient malevolent race that would become a major threat, the overall story of the show being less reliant on story-of-the-week episodes and more of an overarching story arc, etc.), asserting that Paramount had rejected J. Michael Straczynski's proposal of Babylon 5 to them in the late 80's, but used certain details of the pitch by inserting them into the story/premise of Deep Space Nine. There was a concerted effort to bury the hatchet, especially by having Majel Barrett (widow of Gene Roddenberry) appear on Babylon 5 as an alien prophetess who spoke on behalf on her recently deceased husband (an obvious nod to Roddenberry who had passed away a few short years before her appearance).
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 because the "flight" cables were too difficult to rig. However, the idea was revisited for a single episode in season two featuring a guest character ( Star Trek: Deep Space Nine: Melora (1993)).
After production ended and the sets were dismantled, the Defiant bridge set was declared "fold & hold" and placed in storage. It was redressed and used 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).
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 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.
The uniforms initially worn on DS9 were designed to look different from those worn on its parent show, Star Trek: The Next Generation (1987), with a colored shoulders and a gray undershirt. 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 (now with gray shoulders and colored undershirt), 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).
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 none of the Trills ever mentioned concerns with being transported.
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.
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.
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.
Colm Meaney was initially reluctant about signing onto the series. Meaney was comfortable playing O'Brien on an episode by episode basis for Star Trek: The Next Generation (1987), and at the time was unsure if he wanted to play a full time television role.
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).
The Bajoran monetary system uses the Lita as currency. The Lita is actually the name of the currency of Lithuania. This nation was occupied by the Russians during the years 1795-1918 and again 1940-1991, much as Bajor was occupied by the Cardassians.
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.
Majel Barrett guest starred in a handful of episodes reprising her role as Lwaxana Troi from Star Trek: The Next Generation (1987). This would make Deep Space Nine the last Star Trek series or project in which Barrett would make an onscreen appearance. Barrett would continue to play the computer voice for DS9 and Star Trek: Voyager (1995), and would go on to do so for Star Trek: Enterprise (2001) and the Star Trek (2009) movie reboot. Through Deep Space Nine, Barrett played onscreen roles in each Star Trek incarnation.
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.
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 - an idea which Gene Roddenberry conceived for the original Star Trek (1966) but never found an opportunity to use - although this was not explicitly stated on-screen until Star Trek: Enterprise (2001). 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).
Constable Odo was originally envisioned as a young Clint Eastwood type. When Rene Auberjonois was called in for his audition, the casting director told him that none of the previous actors had been 'grouchy enough'. So Auberjonois improvised his lines using his most gravelly voice, and secured the role.
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 character of Morn, the Lurian bar patron who 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 (1982). Morn is an anagram of Norm.
This is the only "Star Trek" TV series not to have any human females as part of the main cast (with Kira being Bajoran and Dax being a Trill). Kasidy Yates and Keiko O'Brien were the only human female recurring characters in the show.
With the show debuting shortly after the 1992 Presidential Election, some TV viewers who were largely unfamiliar with the Star Trek franchise mistakenly believed that Quark was a lampoon of Independent Presidential Candidate Ross Perot (Short height, large ears, financially minded/obsessed). That was obviously not the case as the Ferengi had first appeared in Star Trek: The Next Generation: The Last Outpost (1987), at least four years before Perot announced his candidacy.
The jars of "pills" in Dr. Bashir's office were actually filled with M&Ms. In many instances during the early episodes the level of the pills would change between shots because crew members kept stealing them. The problem was solved by epoxying the lids in place.
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.
The U.S.S. Defiant was first envisioned to look like a beefed-up version of a runabout. When that did not work out, they used an existing design for an alien cargo ship as basis, and developed it as a battleship. It was first called the U.S.S. Valiant, but producer Rick Berman vetoed any name beginning with letter V since he didn't want to create confusion with Star Trek: Voyager (1995), which they were setting up at the time. Defiant was chosen because like Enterprise, it was a name that had been used for a ship in Star Trek (1966) as well.
Season 5's Star Trek: Deep Space Nine: Trials and Tribble-ations (1996), which was a time travel story, was written to mark the 30th anniversary of the "Star Trek" franchise. Instead of bringing back William Shatner, Leonard Nimoy and the original cast due to their ages, it was decided with blue screen and computer technology, the cast would interact with footage from Star Trek: The Troubles with Tribbles (1967) and it was written into the script that the DS9 crew travel back through time to the Tribbles mission in 2268 and prevent Arne Darvin from assassinating Captain James T. Kirk and changing the timeline.
In the narrative behind Commander Sisko's deep hatred for Captain Picard: Sisko blames Picard for the death of his wife Jennifer, whom was killed in the Battle of 359, which Picard had been abducted and assimilated by the Borg.
Terry Farrell admitted in an interview that Season 2's Star Trek: Deep Space Nine: Blood Oath (1994) is a favorite episode, and she is a big fan of it because it revealed a great deal about Jadzia Dax.
Some fans of the show were confused by Jadzia and Curzon Dax and that Commander Sisko calls Jadzia Dex "Old Man" and wrongly assumed that Curzon Dax and Jadzia Dax are the same person. It's established in the series that Trills have slug-like "symbionts" in their abdomen, which is transplanted from Trill to Trill upon death. The Dax symbiont was transplanted into Jadzia when Curzon Dax died. When the symbiont is transplanted into the new Trill host, the new Trill host inherits the previous host's memories. Jadzia is not Curzon, but a part of him lives on within her. Jadzia was 28 when she became the new host of the Dax symbiont and Curzon was over 100 at the time of his death.
Kevin Grevioux played the recurring part of a nameless Security Officer in the first three seasons of Star Trek: Deep Space Nine, but was only given a name in the official Star Trek Customizable Card Game: Taylor Moore.
Brock Peters, who appears in several episodes of as Captain Benjamin Sisko's father, Joseph Sisko and another character called "Preacher", previously appeared briefly as Admiral Cartwright in Star Trek VI: The Undiscovered Country.
The trivia items below may give away important plot points.
Regarding the end of season 6: Terry Farrell left the series when her contract expired and the producers were unwilling to meet her demands for her to stay on for another season. Farrell later claimed that she would have been willing to make guest appearances in Season 7 but never did as her character was killed off.
Regarding the end of season 6: Terry Farrell was the only regular Star Trek actor not to return in any way after her character was killed off. Leonard Nimoy's Spock was resurrected, and Denise Crosby Tasha Yar made appearances in flashbacks and alternate universes, and Crosby also appeared as Tasha's adult daughter.
Regarding the 7th season: 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 in Star Trek: The Next Generation: Data's Day (1991) as a recurring character on Star Trek: The Next Generation (1987)). In addition, Sisko was the first Star Trek Captain to be permanently married when he wed Kassidy Yates.
Benjamin Sisko is the only commanding officer of a Star Trek series that doesn't start out with the rank of captain at the beginning of the series. For the first three seasons Sisko held the rank of commander. It wasn't until the Season 3 finale, Star Trek: Deep Space Nine: The Adversary (1995), when he was finally promoted to captain.
Regarding season 6: 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 (or species) romances, notably married couples O'Brien and Keiko, and Rom and Leeta.
Regarding season 7: A number of fans were initially reluctant to accept Nicole de Boer as the new host for the Dax symbiont after Terry Farrell's departure from the show, rather derisively referring to de Boer as "Ally McTrill", due to her slightly neurotic personality resembling Calista Flockhart's Ally McBeal (1997).