Early-Installment Weirdness: Gagh, the Klingon worms, were called Racht in the first two seasons. Gagh had already been established on TNG.
In the early seasons, the Bajorans were shown to applaud with both palms, though the show would later establish that Bajorans applaud with the back of one hand into the palm of the other.
In her early stage in her development (Terry Farrell was the last actor cast with little prep time before shooting began) Dax walks around with her hands behind her back like a holy woman at Lourdes. Though it could be argued that Curzon and the others start to influence her behavior more.
Earn Your Happy Ending: Played very straight by Nog and Jake in "In the Cards", with hilarious consequences. They go through a lot to get that baseball card. But by the end, everyone on the station feels better, not just Sisko. They also do tons of wheeling and dealing to get five bars of latinum in "Progress", while Nog does the same solo in "Treachery, Faith, and the Great River" (at the risk of poor O'Brien almost getting his head taken off by Kira, Worf and Martok).
Easily Conquered World: Betazed was taken over during the Dominion War with minimal effort and nobody around to even try and put up a fight.
Either this, or could be an example of Curb-Stomp Battle, something the Dominion is fond of doing. Either way, it's used to demonstrate how badly the war is going.
It was specifically stated that fleet supposed to protect it was off at exercise, and planetary defense systems were "obsolete and undermanned".
Elevator Going Down: the turbolift version. After some major flirtation, Bashir and Ezri end up making out in the turbolift on the way to Ops. When they get there (and they keep kissing) a bemused Worf sends them back down rather than interrupt them.
"Past Tense", where Sisko's presence in the past caused the premature death of an important historical figure a few days before he was supposed to die heroically, forcing Sisko to impersonate him.
Commented on in "Little Green Men". Nog was studying Earth's history, and when he encountered an entry about the historical figure, passed comment about how closely Sisko resembled a picture of him (the picture, of course, being that of Sisko).
Sisko also, at one point, gets kidnapped by Miles 'Smiley' O'Brien from the Mirror Universe, because Mirror-Sisko was killed-in-action and they need someone to convince Sisko's Mirror-wife to join the rebel cause. Naturally, it works. A subversion, though, since she admits she realized pretty early on that he wasn't her real husband, mostly because he wasn't a jerkass. But he ended up legitimately convincing her.
Emotional Maturity Is Physical Maturity: The Jem'Hadar are all much younger than they look. One episode with a young Jem'Hadar that was separated from the rest of its brood indicates that they grow to full physical and emotional maturity within a few weeks. The few occasions we see into their behavior does bring this into question, especially the childish bickering between the Alphas and Gammas.
They acquire knowledge rapidly during their development, but not necessarily wisdom, this explains both the seeming maturity and the bickering. The strong code of honor and the conditioning for obedience makes them look mature until they encounter a situation not covered by their conditioning.
Endangered Soufflé: Subverted, where they sneak weapons into a prison under the pretense of delivering a souffle, and when a guard demands to investigate it, they warn him to be careful with it...right before they knock him out with the Off-Button Hypospray, causing his head to fall into the souffle and crush it.
Dukat and Kira in "Indiscretion" and "Return to Grace"
Dukat envisions himself and Sisko as something like this in the episode "Waltz". The truth is he's just nuts and running out of self-delusions.
The Alpha Quadrant Alliance is this. The Federation, Romulan Star Empire, and Klingon Empire all join forces against the Dominion onslaught.
Establishing Character Moment: Most notable with Kira, as our first glimpse of her is a shouting match with the provisional government. That fire would remain a centerpiece of her character for the rest of her life. (As would her continuing clashes with the provisional government, for that matter).
Also Sisko, when confronted by Q (see above).
Odo's grabbing a thief without using a weapon and shouting "Who the hell are you?" to Sisko is another one.
Experimental Archeology: The plot of the episode, "Explorers," in which the Siskos go solar sailing in a light ship of ancient Bajoran design and inadvertently prove the idea that ancient Bajorans could have reached Cardassia.
Gul Dukat. Tora Ziyal is willing to give him chances he doesn't deserve and almost always forgives him, no matter what he does or how he treats people (including her).
Enabran Tain has Garak's loyalty even despite the Noodle Incident that caused Tain to feel so personally betrayed by Garak that he exiled him. Even knowing Tain was Garak's mentor, Odo cannot understand why Garak's loyalty is so unshakable he'll risk his very life to try and help Tain. Tain is Garak's father, hence the loyalty.
The Changeling race serves as this for the Female Changeling. In the series finale, she calls off the Dominion offensive and surrenders in exchange for Odo curing the Great Link of the virus and returning to the Great Link, making true a past claim she had once made to Weyoun that she'd give up the Alpha Quadrant itself if it meant bringing Odo home.
Same thing in the episode "Little Green Men", Earth 1947. Once the story reaches Earth, it's a smoke-fest for the next 30 minutes. Every human who has more than 2 seconds of screen-time is seen smoking at least once. The trope is played straight, as part of an AnviliciousTake That at smoking. The Ferengi talk about how humans willfully ingest poison simply because it's addictive, and Quark even tells a General that Humans should stop smoking because it would kill them.
Evil Albino: The main villain in "Blood Oath" is this. He's not even given a name apart from "The Albino".
Evil Is Hammy: Invoked in "Duet" by a Cardassian pretending to be another man who oversaw an infamous death camp. When he dropped his facade, his hamminess was gone.
Evil Is One Big Happy Family: Quoted almost word for word by Weyoun in "The changing face of evil", but actually subverted since Damar betrays him and Cardassia rebels against the Dominion.
Evil Mentor: Tain ( Garak's father) was this to Garak. Also, the Female Changeling serves as this to Odo in "The Search," teaching him about the history of his people and helping him hone his shapeshifting skills.
Evil Sounds Deep: Captain Sisko provides a rare anti-heroic example. Listen to his voice, in the episode "In The Pale Moonlight" particularly, and you may notice he almost always speaks with a dark low rasp when he's going against all his principles and engaging in deceit and treachery.
Evilutionary Biologist: The Founders took control of the Gamma Quadrant through their keen use of genetics. Their foot soldiers, the Jem'Hadar, are rapid-aged to adulthood and fully-programmed with battle prowess. The Vorta lack a sense of taste, restricting their diet to roots and berries (the food they ate before the Founders revamped their DNA), have very sharp hearing to better eavesdrop, and very strong poison resistance to thwart assassinations by poison. And any culture that opposes the Dominion is treated to an outbreak of the Blight.
Exploited Immunity: In the episode For The Uniform, Eddington bombs Cardassian colonies with chemicals that are harmful to them, but not humans. In response, Sisko bombs a Maquis colony in kind, threatening to continue doing so to force Eddington to surrender.
Exposed Extraterrestrials: Odo is technically naked most of the time, but since he's a shape shifter it looks like he's wearing clothing and it's never really commented on. It's also most likely he doesn't have any parts to expose anyway until he wants them.
When the Great Link transforms Odo into a biological humanoid in "Broken Link," he is ejected from the Great Link naked, in a literal example.
Fake Defector: Holographic simulation Garak in "The Search: Part 2".
Fake Memories: The trope is toyed with in "Hard Time" but ultimately averted when Bashir determines that O'Brien actually did experience a sped up simulation of some 20 years in prison (rather than simply having had those memories implanted). So the memories are real and can't just be removed without wiping the rest of the Chief's mind too.
Fan Service Pack: After the season 4 opener, Kira received a tighter uniform with no shoulder pads, and high heels. (The effect was somewhat reduced mid-season when Nana Visitor became pregnant; see Real Life Writes the Plot below.)
Fantastic Caste System: The Bajorans used to have one, but it was abandoned during the occupation. Subtle references are made to it through-out the series before it was explicitly revealed in an episode where it is temporarily revived. Its enforcement by law would have threatened Bajor's application to join the Federation (which doesn't allow caste-based discrimination).
In the episode "Accession" a time-displaced Bajoran poet who claims to be the Emissary instead of Sisko tries to reinstate the caste system. The results are Played for Drama with Kira being visibly uncomfortable with lower-caste Bajorans deferring to her and her own struggles with her caste-as an artisan with zero artistic talent-which ultimately leads to a vedek killing a man because his family was considered unclean.
Fatal Family Photo: Lt. Hector Ilario shows a photo of him with his friends from the academy to Ezri Dax, before bidding her goodnight, near the start of the episode Field of Fire, when she wakes up the next day it's been discovered that the Ilario has been shot dead. It turns out by the end of the episode that the link between the victims is their smiling photos with family and friends.
Fantastic Slurs: Cardassians are occasionally referred to as "Cardies" and "Spoon heads." "Shifter" "and "Changeling" are used to refer to Odo's species, though the latter name was later adopted by the species as their name.
A Starfleet officer even referred to Cardassians as "spoonheads" in "Empok Nor", though this was in the background. But it's understandable in context; the crew is being stalked by fanatical Cardassians at the time.
O'Brien would occasional mutter "Cardie bastards", although its been long established that his dislike of Cardassians is more due to unpleasant memories from the Federation-Cardassian war and holding them responsible for him having to take a life for the first time.
The Ferengi have a particularly snide way of pronouncing "hew-mon" that makes it clear they intend this. Jake reclaims it occasionally.
It's fairly intentional among Ferengi. Quark often pronounces "human" correctly (though not always), although that could also stem from his living among them for so long. In general, he only uses "hew-mon" if he's making an observation on the race as a whole (such as in The Siege of AR-558").
The way Brunt calls Quark a "philanthropist" and the way he reacts in the episode "Body Parts" implies this is one among Ferengi.
The Fellowship Has Ended: Half of the crew goes their separate ways in the war's aftermath, making for one of the more melancholy Trek finales. Kira becomes El Jefe, Bashir and Ezri stick around (with Ezri humoring Julian by taking over for O'Brien in the holosuites), and Quark does what he always does, which suits him fine. "I don't like change."
The Romulans amend the Treaty of Algeron, allowing the Federation to use a loaned cloaking device in exchange for intel on the Dominion. Originally the device could only be used in the Gamma Quadrant, but this was further amended so it could be also used in the Alpha Quadrantnote That's the going theory, anyway. The first amendment is explicit, but they later start using it in the Alpha Quadrant with no explanation given, and the Romulan liaison they had to observe the use of the cloaking device quietly disappears from the show..
When the Federation-Cardassian Treaty was being undermined (with the Cardassians oppressing former Federation citizens), the Federation failed to effectively deal with the issue. As a result, the Maquis resistance force begin operations.
Find the Cure: Section 31 creates a disease designed to annihilate the Founders in order to bring down the Dominion and end the war. In order to transmit the disease to the Founders, they use Odo as a carrier. This leads to three episodes of this for Dr. Bashir.
Subverted in "The Quickening." Bashir comes to the aid of a planet that was infected with a plague two centuries ago by the Jem'Hadar, expecting to swoop in with his genius and his gadgets and save the day with another miracle of 24th century Starfleet medicine. It doesn't work out that way. He does, however, find a vaccine that, when administered to pregnant women, makes their children immune to the disease, giving the civilization hope for the future.
First Episode Spoiler: The station's relocation to near the wormhole. Cleverly, the pilot used a version of the opening credits that did not show the wormhole opening, which they would ever afterwards.
Helpful hint: If describing the show to a potential newcomer, say the station "is on the edge of Federation space". This sets up almost every plot point plausibly enough for a non-viewer. On the other hand, anyone interested in learning more about DS9 probably already knows there's a wormhole.
First Name Basis: Sisko and Jadzia, Bashir and O'Brien, Dax and Kira, Jadzia and Bashir, Odo and Kira eventually.
Bashir tries to establish this early on with O'Brien, insisting that he call him Julian rather than "sir". At this point, O'Brien still found him incredibly irritating and so makes the first name sound even more formal and awkward than "sir" ever could. At the end of the episode, Bashir gives in and tells him to just drop it and address him how he likes.
Fixed Forward-Facing Weapon: The U.S.S. Defiant is an escort cruiser purposefully designed for combat, containing 4 fixed-forward pulse phaser cannons and 4 quantum torpedo launchers (2 fore, 2 aft).
Flanderization: When he was first introduced in "Equilibrium," Joran Dax was merely a mentally unstable man who killed a few people out of self-preservation. The episode treats him as a tragic and sympathetic character. In his later appearances, he is portrayed as a vicious serial killer.
Flaunting Your Fleets: There were a few shots like this, especially later in the series as the Dominion War (and the CGI) picked up.
Flip Personality: There's an episode where other characters voluntarily share their bodies with the personalities of previous Dax hosts. Quark is very uncomfortable with the personality he's hosting and keeps emerging to complain.
Food Pills: It is established that Starfleet field rations A) superficially resemble beef jerky, and B) are generally loathed by most Starfleet officers—except Chief O'Brien.
Foregone Conclusion: Will Worf and Jadzia get married in "You Are Cordially Invited"? What do you think?
Possessed!Kira in Dramatis Personae acts a lot like her Mirror Universe counterpart, alternatively seductive and ferocious.
In Season 2's The Maquis, the Badlands are introduced with Sisko noting that a number of ships have been lost in the plasma storms over the last year. The mystery of the missing ships foreshadows the events of Star Trek: Voyager.
It's uncertain whether the writers had already decided that Dr Bashir was going to be a secret genetically engineered human, but it certainly appears to be hinted at in the fourth season episode Our Man Bashir when he calmly and effortlessly shoots Garak's neck, resulting in a flesh wound that could well have been lethal if he'd intended, but instead merely clipped the flesh.
In Sacrifice of Angels, the Prophets tell Sisko that he will not find peace on Bajor, and the female Changeling suggests that Odo will one day join the Great Link again. Both of these predictions come true in the series finale.
In "The Sound of Her Voice", O'Brien talks about how one day, someone they know is going to die. The camera pans to Jadzia, who dies the next episode.
Admiral Ross is no slouch in this department either, especially by the usual standards we've come to except from Starfleet flag officers.
Framing Device: The story of "Trials and Tribble-ations", being told by Sisko to Starfleet Temporal Investigations.
"Necessary Evil" has this same device but in a more roundabout way. Odo is narrating the present-day investigation, but his flashbacks are not directly presented as a "story" to another character or the audience. Odo specifically states that he hates keeping records or logs, so his memory itself is his "diary", so to speak.
"In The Pale Moonlight" is framed as Sisko recording a log entry about his actions (which he then deletes at the end of the episode).
A rare case of two simultaneous examples occurs in "Our Man Bashir". Bashir and Garak are stuck on a James Bond style holodeck novel with the safeties off and the rest of the crew trapped inside. Garak wants to leave the holodeck but Bashir shoots and just clips him. As a result Garak agrees to continue having seen Bashir's determination to save the rest of the crew. However, when Garak calls for the door to leave he does it in an unnecessarily long winded way which gives Bashir time to shoot, showing that Garak was testing how far Bashir would go and if he would be prepared to kill him. On the other hand, as we later find out, Bashir is genetically modified and clipping Garak was an easy shot for him. So Bashir was fully in control of the situation and only made Garak think that he was prepared to kill him. Fridge Brilliance all around.
When Vedek Winn asked Mrs. O'Brien not to teach anything about the wormhole, wanting Bajoran spiritual beliefs taught along with Federation science, Keiko knew exactly where this would lead and asked "what about when we get to evolution, or the creation of the universe?"
Get a Hold of Yourself, Man!: "The Die is Cast": Just before the ship is destroyed, Garak gets Odo to the runabout but goes back for Tain, who's trapped on the bridge in a state of shock. Garak can't talk sense into him and can't abandon him. Odo has to punch Garak unconscious to get him off the ship. Later, Garak does acknowledge that Odo's action was the only way to bring him to his senses and that it saved his life as a result.
Getting Crap Past the Radar: From "The Begotten" Doctor Bashir to Odo: "You need to relax, I told you that last week." Odo: "And it helped, that and the prune juice."
Many people seem to enjoy the holosuite program "Vulcan Love Slave" - there is even a "Part 2".
In The Wire, Quark tries to get some information from a certain Cardassian officer named Bohica* Bend Over, Here It Comes Again, but it's way above his pay grade.
Gilligan Cut: Kira claims to be always diplomatic. Cut to her handling affairs...
When trying to procure a baseball card for his father, Jake and Nog find that the owner has gone missing. Recognizing a Bajoran speaking to Kai Winn as a guy from the auction bidding on the same lot, they suspect that Kai Winn is responsible and prepare to question her about it. Cut to them being berated in Sisko's office for accusing the Kai of theft and kidnapping.
During "In Purgatory's Shadow" Worf and Garak discover that Bashir has been replaced by a Changeling back on DS9. After the real Bashir comments that he can only imagine what his imposter must be up to and Worf says they must warn Captain Sisko before he can carry out his mission, we cut back to DS9 where the Bashir Changeling is delivering a plate of sandwiches to O'Brien and Dax. Darkly subverted when the Changeling later DOES carry out his mission—sabotaging the graviton emitter that O'Brien and Dax were working on in that very scene.
God Emperor: The Founders of the Dominion use this to keep control of the Vorta and Jem'Hadar.
Well, that and genetic tempering, cultural manipulation, and drugs.
Godwin's Law: Dukat is compared to Hitler in some places. Nana Visitor, who plays Kira, said that Kira sees Dukat as Hitler, and nothing will ever change that.
Leads to a Crowning Moment of Funny at the end of "Who Mourns for Morn?" Quark believes that he has finally avoided all the other people trying to claim a tremendous stash of stolen latinum. Only to break one open and realize "There's no latinum in these bricks! There's nothing here but worthless gold!" Cue Big "NO!" as he frantically flails around in a pile of gold dust.
Then Quark remembers that some primitive cultures still place great value in gold.
Go Mad from the Revelation: A slow working version. During the Dominion War, Garak was key to Starfleet Intelligence in breaking Cardassian communications. He knew his actions were for the very best in the long run but with every transmission he translates he is killing more and more Cardassians. This builds over several years until the first bout of madness is his claustrophobia going to extreme levels where he cannot even be on the station. He is treated by Ezri Dax and they discover the truth before he goes mad any further.
Good Hair, Evil Hair: The Cardassians and the Founders all sport the same slicked-back hairstyle. Notable exceptions are Gul Dar'heel's helmet hair from "Duet", and the varied hairstyles seen on Cardassian women.
Government Drug Enforcement: The Founders used Ketracil White, an addictive performance enhancer and vital nutrient supplement, to control their Jem'Hadar supersoldiers. Without it, they will die—but not before going into an uncontrollable berserker rage.
G-Rated Sex / Better Than Sex: Changeling linking. During the occupation of Deep Space Nine in "Behind the Lines" and "Favor the Bold," Odo and the Female Changeling spend days behind closed doors linking. The Female Changeling insists that sex pales in comparison to it — and since she's done both with Odo, she means this literally.
Ham-to-Ham Combat: It's Star Trek; a certain amount of hamminess is to be expected. But the truly epic argument between Quark and Ishka in "Profit And Lace" really takes the ham-flavored cake with bacon frosting.
Hammerspace: In "Defiant", after Kira releases the Defiant's command codes, Riker fires a phaser at her to stun her. He wasn't wearing a phaser. And it's a type-two phaser, not the smaller type-one which someone could conceivably conceal in their palm.
This is subverted in the episode "For the Cause", in which Eddington also sneak-attacks Kira; however, he and the other Starfleet Security officers were already armed on this occasion.
Justified in the episode "Badda-Bing Badda-Bang": when Vic asks how they plan on just walking away with a million dollars, Odo explains that he'll hide it inside himself.
Hand or Object Underwear: In "Doctor Bashir, I Presume", at one point Leeta gets so excited by Zimmerman's offer of her own cafe to run that she walks over to him, all excited, completely forgetting that she was just wearing a towel, isn't anymore, and didn't get around to putting anything else on to replace it yet. When she realizes, she grabs a bouquet of flowers to cover her chest with as she retreats to the bedroom to get dressed.
Hate Plague: in Dramatis Personae, a telepathic thingy that caused the extinction of a Gamma Quadrant species turns the crew (except Odo) into a pack of raging factional paranoids.
Heroic BSOD: Sisko has one at the end of the season 6 finale, first few episodes of season 7 were devoted to showing him getting through it.
In "For The Uniform", he faked one in order to bring Eddington down. And did it extremely convincingly.
Quark got this, but not from a failure. When he just opened fire on two Jem'Hadar soldiers, killing them and allowing his brother to be saved, he stands there shocked that he did something like that.
Played far more seriously in The Siege of AR-558, where Quark spends most of the episode deriding humans' violent and bloodthirsty nature when they are threatened or deprived of their creature comforts. When Quark kills a Jem'Hadar to defend his wounded nephew, Quark shows signs of Heroic BSOD as he realizes he has become just as violent.
He Who Fights Monsters: The whole Section 31 genocide on the Changelings and the Federation's tacit approval leads some characters to ask what makes the Federation so much better than the Dominion if they're willing to stoop to committing the same kind of war crimes.
"Hey, You!" Haymaker: Upon realizing that Garak blew up a Romulan senator's shuttle, Sisko barges into his shop to deliver this greeting.
Hoist by His Own Petard: In the season 1 episode Dax, Jadzia Dax faces murder charges from Ilon Tandro, who blames Curzon Dax for killing his father, General Ardelon Tandro; this bites Ilon in the ass three times.
First, he kidnaps Jadzia instead of asking for extradition despite having an extradition treaty with the Federation, this is because DS9 is technically a Bajoran station, and by sabotaging DS9 in order to kidnap Jadzia, they've given Bajor a perfectly good reason to get involved.
Second, it turns out Curzon was having an affair with the Ardelon's wife, which is not only a motive, but turned out to be his alibi. Ilon went through all that trouble to hunt down his father's murderer, only to find out said murderer was innocent because he was busy banging his mom.
Third, is that the evidence suggesting Curzon betrayed Ardelon, was Ardelon betraying Curzon. Ardelon was regarded as a war hero who was betrayed by one of his inner circle, but Ardelon was the traitor, it just never came to light.
Holding Back the Phlebotinum: Tended to be the show that subverted this the most in Star Trek. You have replicators? Self-replicating minefield. Your transporter accidentally sent you to a parallel universe? The other universe standardized the technology. And if you can transmit hologram packages to the Delta Quadrant, you can probably manage real time holodeck communications in the Alpha Quadrant. They're also the only one of the five shows to actually let their main characters use cloaking technology which was present in all of themnote Although to be fair, they are legally prevented from using it, which was established in TOS. They even let their augment practice medicine openly.
Holding the Floor: In "Looking for Par'mach in all the Wrong Places", Quark demands the Ferengi Right of Proclamation during a duel with a Klingon to give Worf and Dax the opportunity to fix the mechanism that allows them to remote control Quark's body during the duel. The Klingons give it to him as he has respected their traditions and they should respect his, though it's unclear whether this "Proclamation" is an actual tradition or whether Quark made it up on the spot to stall proceedings.
Quark, oddly enough, pulls off a pretty awesome holier-than-thou when he points out to Sisko how, though humans look down upon Ferengi for their Straw Capitalist culture, humans are actually reacting to memories of their own capitalist past and the ugliness that went on in their culture as a result. He follows up by pointing out that Ferengi have managed to avoid that ugliness and brutality through commitment to their principles, such as they may be, making Ferengi superior to humans.
Quark: The way I see it, humans used to be a lot like Ferengi: greedy, acquisitive, interested only in profit. We're a constant reminder of a part of your past you'd like to forget.
Sisko: Quark, we don't have time for this.
Quark: You're overlooking something, Commander. Humans used to be a lot worse than Ferengi. Slavery, concentration camps, interstellar war; we have nothing in our past that approaches that kind of barbarism. You see? We're nothing like you. We're better.
YMMV, one of his examples is that they never had anything like slavery. But ALL Ferengi females are considered property and forbidden to own anything or earn profit. At least until Quark's feminist mother turns out to be the most brilliant business mind of her generation.
Holodeck Malfunction: "Our Man Bashir", sort of. Actually, it was more an example of something going wrong with the transporter, and the holodeck worked to keep the physical patterns of the crewmembers intact. (On the other hand, the holodeck's safety routines did malfunction, so...)
Worf: We were like warriors from the ancient sagas. There was nothing we couldn't do.
O'Brien: Except keep the holodecks working right.
Honey Trap: Played for Laughs in "For the Cause". The first time Ziyal asks Garak out on a date, Quark and Garak speculate about her motives for doing so. Quark accidentally convinces Garak that Kira's come up with a plan to use Ziyal as a Honey Trap to kill Garak on Dukat's behalf.
Honor Before Reason: The aversion of this in "In the Pale Moonlight" results in one of the most respected and controversial episodes of the series.
Hostile Terraforming: Sisko used a specialized warhead to poison the atmosphere in such a manner that it would be uninhabitable for human life, but functional for Cardassian in an attempt to force Eddington to surrender. Though the Maquis did pretty much the same thing (except rendering it uninhabitable to Cardassian life but safe to human) to multiple Cardassian colonies.
Hot Skitty-on-Wailord Action: In some of the Fan Fiction, Odo and Nerys's relationship gets this treatment. Odo's species being shapeshifters, it's speculated by some that he brings certain special skills to the bedroom.
He outright transforms into a cloud of sparkling gas at one point to give Kira an idea of what the Great Link is like. It's safe to say this is not the first (or last) time his shapeshifting skills have been used for kinky purposes. (Apparently, after they were done filming that scene Rene Auberjonois said to Nana Visitor, "God, you make me look like such a great lover!")
Well, he DID have physical sex with the female Changeling at one point, just to show her what it was like for "solids".
(After discovering that their treatment of Cardassian civilians had caused the Cardassian fleet to defect)
Female Changeling: I want the Cardassians exterminated.
Weyoun: Which ones?
Female Changeling: All of them. The entire population.
Weyoun: That could... take some time.
How the Mighty Have Fallen: This is the general attitude other Cardassians inside the Union have for Garak. Gul Toran even says this line verbatim in "Profit and Loss".
How Would You Like to Die?: When Dr. Giger asks Jake and Nog, "Do you want to die?" in "In the Cards", Jake and Nog are taken aback and take it as this threat. Subverted when it turns out it's just the opening line of Giger's sales pitch for the Cellular Regeneration and Entertainment Chamber.
Sloan in "Inter Arma Enim Silent Leges". When Bashir expresses concern that Koval, the head of the Tal Shiar, has expressed interest in obtaining and deploying bioweapons, Sloan says "Yes, these are not nice people." About two minutes later, Sloan is asking Bashir if there's any known way to cause the terminal illness that Koval is suspected to have to unexpectedly begin to progress faster.
Triply so when you consider that Section 31, and Sloan in particular, are responsible for the disease killing the Founders.
I Am X, Son of Y: "I am Quark, son of Keldar, and I have come to answer the challenge of D'Ghor, son of... whatever."
D'Ghor's reaction suggests that this is a deadly insult to a Klingon.
And of course, "I am Worf, son of Mogh!" This is actually quite a common introduction among Klingons.
Notable in that when Alexander does not introduce himself in this fashion, it signifies a large rift between him and his father.
Idiot Ball: Sisko and Kira in "Resurrection". We're at war, someone's beaming into Ops and we have no idea who they are or where they're coming from. Don't have the guards rush over there or anything, just assume it's harmless. Surprise, the bad guy has a phaser and takes Kira hostage.
Odo in "Invasive Procedures." After finding Quark messing around in an airlock with the flimsy excuse that he is "meditating," he simply orders him out and completely fails to actually look around the airlock (where the only means Quark took to hide a signal device was to stick it on the same wall as the door). There is really no way Odo should fail to do this, given that suspicion and investigation are hallmarks of his interaction with Quark.
I Don't Pay You to Think: In the episode "Bar Association," Quark tells Leeta "I don't pay you to think. I pay you to spin the Dabo wheel."
I Don't Want to Ruin Our Friendship: Shakaar worrying to Odo about starting a relationship with Kira. Later, Odo and Kira. Even later, Bashir and Ezri Dax, for about a day, until they start making out in a turbolift.
Also the plot of "The Magnificent Ferrengi." Except replace "Wife" with "Girlfriend," and "Your" with "Grand Nagus." Also it's Quark and Rom's mother as well.
Insistent Terminology: The Dominion is fighting for control of the Alpha Quadrant despite the fact that two of the four major powers they're dealing with exist primarily in the Beta Quadrant, and the third half so. Granted, the Bajoran Wormhole and the Cardassians are based solely in the Alpha Quadrant, but still, you'd think they'd occasionally talk about the Beta Quadrant given that both the Romulans and the Klingons mostly live there.
I Shall Return: Sisko's speech at the end of season 5, where he tells the people of DS9, "I will not rest until I stand with you again," before leaving to fight the Dominion.
It Has Been an Honor: Martok's adjutant to Kor in "Once More Unto The Breach" when Kor decides to take Worf's place commanding a suicide mission.
It Will Never Catch On: "Far Beyond the Stars" both plays this for laughs (Shimmerman's character pitches Buffy a few decades too early) and for brutal drama (the magazine's owner cancels the issue rather than publish a story about a black spaceship captain).
Injured Kira to Dax after the crash in "The Seige", but Dax takes her along anyway.
Dax is bleeding to death in "Change of Heart" and Worf leaves her behind to finish the mission. He ends up abandoning the mission to come back for her.
Humorous example in "The Ascent", where Quark hauls the injured Odo up a mountain on a stretcher. When Odo protests, Quark emphasizes his reasoning: Odo's along for emergency rations; if he dies, he's food.
Lampshaded in Season 7 when Worf gets shot as he and Ezri try to escape the Dominion:
Worf: Leave me!
Ezri: Shut up!
Icon of Rebellion: In a story arc, Bajor is threaten by a nationalistic group called the Circle. These extremists would spray paint their symbol as vandalism or in their headquarters.
Idiot Ball: The Klingons use of the Bat'leth in battle. A particularly egregious example occurs "The Way of the Warrior" where they fail to remember that just because Humans Are Diplomats, doesn't mean that in a fight they aren't the Combat Pragmatist. After gunning down the first wave of invading Klingons on the station, they simply take their fallen Bat'leths and use them to slaughter more invading Klingons. Some episodes did try to make them seem more pragmatic with Worf and Jadzia debating Bat'leth tactics, but even in those scenes it's hard not to notice how cumbersome the weapons are.
In "The Darkness and the Light" a Serial Killer targets the surviving members of Kira's old Bajoran resistance cell, eventually luring the very pregnant Kira to his hideout, stunning her, and then attempting to cut Kirayoshi out of her (the intent was to save the innocent baby and take revenge on Kira). She manages to turn the tables and shoot him.
"Rules of Acquisition" is a typical Ferengi episode that just happens to feature the first mention of the Dominion.
"The Assignment" appears to be a generic Monster of the Week story at first. However, it introduces the Pah-Wraiths, the enemies of the Bajoran Prophets, who eventually become a key part of the main plot.
Insistent Terminology: DS9 is not a Federation station... it's a Bajoran station under Federation administration. This is repeated several times by Sisko and especially Kira in the early seasons.
Insufferable Genius: Bashir, especially in early seasons. Arguably got worse after the truth about his genetic enhancements came to light. This was lampshaded by Garak in "A Time To Stand".
Interspecies Romance: Since the cast is comprised of several different species, there are a lot of these. Jadzia is fancied by both Quark and Bashir, and ends up marrying Worf; Ezri, in turn, eventually enters into a relationship with Bashir. Dukat has a thing for Bajoran women - he had several Bajorn mistresses and has a half-breed daughter in the form of Tora Ziyal - and he lusts after Kira. Odo's been in love with Kira for quite a while as well. Quark has a brief marriage and recurring relationship with Grilka, a Klingon woman, as well as an old flame in the form of Natima Lang, a Cardassian scholar. Rom pines after and eventually marries Leeta (a bajoran). Ziyal has a crush on Garak, who possible reciprocates, and Garak hassomething that's never quite made clear with Bashir. Phew.
The Intern: Bashir, for the first season or so. He's in charge of the infirmary because they're so short-staffed and nobody wanted the job, anyway.
Intimate Marks: An exchange between Jadzia and a Boy of the Week provides the page quote. Starting with this series Trills all have dual rows of spots starting at their foreheads and continuing down their sides to their feet. A minor Running Gag is that non-Trills would like to know just how far down the spots go. This was enforced over the Rubber-Forehead Aliens look used in the Trills' debut in TNG: "The Host" because the DS9 TV crew thought the TNG makeup made Terry Farrell look ugly.
Intrepid Reporter: Jake, who stays behind after the Dominion takeover of the station.
According to the Expanded Universe, this is based upon the Cardassian name for Bajor: Terok.
It's All About Me: A plot point of Season 6's "In the Pale Moonlight". Sisko realizes that this is how to appeal to the Romulans to enter the Dominion War. They won't do it help their oldest rivals…but they would do it to protect their own interests.
It Is Beyond Saving: Ezri believes this about the Klingon Empire, in stark contrast with Jadzia's tendency to romanticize it.
It Tastes Like Feet: Kira complains that some medicinal herbs Bashir gave her for her pregnancy "taste like something that crawled out of Quark's ear."
Jerkass Has a Point When a Cardassian starts killing off Kira's friends from the resistance, their deaths are horrific and tragic. And then we meet the Cardassian who did it, who is mumbling about evil and good, dark and light etc. and he seems insane... And then we find out that he was actually just a butler in the Cardassian occupation who had never hurt a Bajoran, and who was horribly disfigured when Kira bombed the house of a significant Cardassian official in an assassination attempt. In doing so, she killed his family, his children, and 12 others and crippling 23 other Cardassians who were completely uninvolved. In return, the Butler who was killing off her friends had only killed the five who were involved in the attempt and was very careful not to hurt any innocent people. His final speech to Kira is rather damning and casts a lot of doubt on her actions and motives in the Resistance:
By the end of the episode, Kira is questioning herself on what happened, and how she ruthlessly manipulated his sense of morality to survive.
Kai Winn has a point when she calls Kira out on her belief that only the members of the Bajoran resistance fought against the Cardassians, reminding the Major that she was arrested for teaching the word of the Prophets and was in a prison camp for five years, subject to beatings and with only her faith and courage to protect her.
The Judge: Els Renora in "Dax", and Makbar in "Tribunal".
Jurisdiction Friction: In "Defiant", when Gul Dukat wants to send Cardassian warships to patrol a certain sector, the resident Obsidian Order observer tells him in no uncertain terms that that sector is under direct control of the Order, and any ship sent into it—including Cardassian warships—will be destroyed.
Kangaroo Court: The Cardassian legal system. Verdicts are determined in advanced and the accused is "always guilty." Your legal counsel is there to help you accept your guilt so you can demonstrate remorse for the audience. All this to assure Cardassian citizens that justice is unwavering, swift, and perfect.
Kavorka Man: Morn got a lot of action for a bald, acne-ridden walrus thing. Supposedly, women find him to be a great conversationalist.
A Running Gag is Jadzia rejecting advances from various guys, yet agreeing to go out with Captain Boday, an Übermensch who happens to have a see-thru head.
Jadzia: He happens to be brilliant; his brain is twice the size of yours and mine combined.
Kira: I know, I've seen it.
Kill the Poor: In a Time Travel episode where Sisko, Bashir, and Dax accidentally travel back to Earth Twenty Minutes into Our Future. Sisko and Bashir are assumed to be homeless by the police who find them and they are sent to an interment camp for the indigent. The government of the time claims that it's a progressive measure to help the less fortunate, but Sisko points out that it's really just a way to sweep the poor under the rug so other people don't have to think about them.
Killing For A Tissue Sample: In the episode "Who Mourns for Morn?" a group of thieves show up on the station to get at Morn's horde of Gold Pressed Latinum from a heist they had all participated in years earlier, and which Morn has willed to Quark. The delivery is coded to Quark's thumbprint, and one of the thieves threatens to kill Quark and take his thumb if he doesn't cooperate. One of the other thieves points out that it'd be more than a little suspicious if they showed up with a bloody severed thumb to get at the delivery.
Kinetic Weapons Are Just Better: The prototype TR-116 Rifle. Designed to operate in environments where energy weapons are unable to function, less unwieldy than a phaser and can be easily modified with a transporter to allow it shoot through walls. Starfleet apparently refused to mass-produce the weapon because it actually worked!
Kiss Diss: Kasidy does this to Sisko once after he apologizes for being afraid of commitment.
Klingon Promotion: Multiple times, including one Ferengi episode, but most notably with Gowron's removal.
Ferengi don't actually practice it, and the guy who tried it was dismissed as a complete idiot. Though he might have gotten the job had he actually succeeded, the fact that he failed marked him as too incompetent to be trusted to do the job right.
It was the way he did it that was the bad part. As Grand Nagus Zek said: "You don't seize power! You build it up, through buying and conning and profit! What good is being in charge without the latinum to show for it?!" This was before the Nagus knew Quark was more than a pushover with just a bar, and he was meant to be a convenient patsy for the real heir to prove himself against.
Laser-Guided Karma: The Federation's "Section 31" creates a plague to wipe out the Changelings and win the war. It is ultimately successful, as the Changelings end up bartering peace in exchange for a cure. This from a species whose geneticists unleashed plagues on disobedient worlds.
Damar kills Ziyal for betraying Dukat and not siding with the Dominion. Then, in the series finale, Damar himself is killed because he rebels against the Dominion.
Last Day to Live: Quark is told he's contracted a deadly disease. In an effort at settling his debts and earning a place in the Ferengi profit-based afterlife, he sells his corpse. Of course, after he learns that he's going to live, he finds out that his arch-nemesis bought said corpse after paying off the doctor to tell Quark he was going to die to begin with.
Last-Second Word Swap: In "Treachery, Faith and the Great River," after Odo protests to Weyoun that he's not a god, he's a security officer, later on Weyoun mentions how honored he is to be in the presence of a g— a security officer.
The Laws and Customs of War: Invoked in "Duet", where the supposed "Gul Dar'heel" points out that while the Cardassians may committed many atrocities during the Occupation, he takes umbrage with the Bajoran's insistence that they were "War Crimes", when as he points out, the Bajoran Government had surrendered to the Cardassians and continued to do so for over 50 years!
Leaning on the Fourth Wall: in the episode "Far Beyond the Stars", Captain Sisko is sent a vision from the Prophets (maybe) of him as a science fiction writer from the 1950s. At the end of the episode, he wonders if life aboard the station isn't the illusion.
In the episode In the Pale Moonlight when Sisko is relating the events of the episode in his personal log the camera is in a generally fixed position right across from him, giving the viewer the impression that it is they who Sisko is speaking to.
In Rules of Engagement, Worf is accused of war crimes and undergoes an extradition hearing. Worf and his crew mates all give their testimony, during which we see the events they're describing. During these flashbacks, the characters speak directly to the camera.
Less Embarrassing Term: During the series finale, Miles and Keiko disagreed on the definition of the scale model of the Alamo that Miles and Julian had built. Keiko insisted it was a toy, while Miles favored the term "miniature". Additionally, in an earlier episode, Worf observed Julian and Miles working on this model and lamented Ezri Dax's affection for Julian Bashir by grumbling "He plays with toys." Ezri insisted "It's a model."
Apparently this is why the Defiant is classed as an Escort Vessel, because Starfleet doesn't want to acknowledge (to itself as much as anyone else) that it's building warships.
Crossroads of Time, which holds the dubious distinction of being the only Platform Game under the Trek banner. This is for a very good reason. Despite being released in 1995 (well after Sisko shaves his head and gets promoted), the story is set immediately after "Emissary" to avoid continuity conflicts. As a downside, the plot is rather inconsequential, though a memorable sequence has Sisko using the Orb of Time to return to his old ship, the Saratoga, as it falls under siege by Locutus.
The Fallen, a First-Person Shooter showcasing the Cult of Pah-Wraiths, who made a few appearances on the show. The plot, a yarn involving Evil Counterpart versions of the Prophets—complete with red orbs and a red wormholes—is based on the Relaunch novel Millenium.
Probably the best-known game, Dominion Wars, which is a mix of Real-Time Strategy and ship-to-ship combat.
Alexander Rozhenko, son of Worf. Yes, you read that right. It gets to the point that they think he's actually drawing bad luck away from THEM, making the ship and her crew luckier by default.
Gaila is this for the team Quark assembles in "The Magnificent Ferengi". He brings no skills or resources to the group, panics during the combat simulations, sleeps when he's supposed to be guarding their hostage, leading to an escape attempt, and accidentally kills their hostage.
The opening credits for the series finale, which features most of the major characters still alive, list nine main actors and fifteen guest stars. And the finale is still missing most of the Ferengi-related recurring characters (Rom, Leeta, Zek, Ishka, Brunt, Maihar'du), who make their final appearance in the penultimate episode.
Throw in the Mirror Universe characters and the number gets almost too high to count.
Locked in a Room: Of the elevator variety. In "The Forsaken", a turbolift malfunction traps Odo with Lwaxanna Troi for several hours... and he needs to regenerate!