Star Trek/Nightmare Fuel



Generally speaking, where British kids had Doctor Who, American kids had Star Trek.

Note: please avoid personal examples, anecdotes and natter. Feel free to tell us about how scary the Borg are, but we don't need to know how they made you hide under the bed.

Let's take it by series:

Original
"Kirk:"
 * There's the classic "The Doomsday Machine", where a giant, bluish-green horn of plenty like machine is consuming everything in its path and the mighty USS Enterprise can't seem to stop it. Not to mention its massacre of the crew of another ship, identical to the Enterprise, whose captain the experience had driven completely mad.
 * Ah yes, the Cornucopia of Doom?
 * No, the Angry Icicle Condom Of Fire.
 * A more sanity-rending horn has yet to be found.
 * Don't forget the very first episode, "The Man Trap", with the shapeshifting alien that sucked the salt out of the victim's body.
 * And the Horta: imagine a giant pizza out to kill you.
 * At least the Horta turned out to be nice -- it turns out she was only defending her babies. The gigantic brain cells of "Operation: Annihilate!", on the other hand...
 * They made Spock scream. Spock. Just trying to imagine the level of pain that would require is Nightmare Fuel all by itself.
 * Moreover, remember that Kirk's nephew, not a Vulcan, is facing potentially far worse pain, should he awaken from his coma -- and despite the joking around at the end, Kirk still has to tell the kid that his parents died in agony, along with a sizeable amount of everyone he knew.
 * In the episode "What Are Little Girls Made Of?" you have Ruk, played by Ted Cassidy (The Addams Family Lurch). Imagine an extremely intimidating giant who is extremely strong and yet also moves with such deadly grace that he can grab you long before you can react.
 * The nightmarish ending of the episode also counts: the Andrea-bot, wielding a laser pistol, utterly at odds with her programming - unsure of whether to love or to kill, embraces her creator, Dr. Korby and Korby pulls the trigger, disintegrating them both. Kirk and Chapel look on in horror, as do we.
 * "A Taste of Armageddon": The people just walk into the disintegration chambers, like they're off to work.
 * The cloud creature in "Obsession". It's capable of space travel, phasers don't do squat against it, it can silently sneak up on its victims pretty much anywhere, and if it catches you it basically sucks out your blood without even leaving a mark. And we're supposed to believe that a simple bomb would kill it in the end... yeah, right.
 * The return of the Cloud Monster of Death was the premise of a DC Star Trek Graphic Novel written, IIRC, by Chris Claremont.
 * Korob and Sylvia in Catspaw relied on classic Nightmare Fuel. Then.
 * And the part where the Red Shirt of the week beamed up to the ship, and then dropped dead? And then a SCARY VOICE came out of his DEAD mouth? Yeek.
 * The Kelvans, who reduced a young yeoman to a polyehdral cube and then crushed her to dust! ("By Any Other Name")
 * And who could forget the Zetarians in "The Lights of Zetar?" Non-corporeal energy beings who zoom around the galaxy so fast the Enterprise can't outrun them, searching for someone to possess so they can live out their lives. And if they can't possess you, they'll just kill you horrifically while trying. The woman who dies on the station spends several seconds with her face writhing uncontrolably and glowing several different colors, possibly in a very great deal of pain, before she dies. Even with the long-out-of-date and obvious special effects, the shot is still unnerving.
 * Charlie X. He can age you, turn you into an iguana or leave your face quite blank, among other disturbing things. But that doesn't really do him justice. Enfant Terrible Reality Warper Stalker With a Crush Mind Rapist, anyone?
 * What about the aliens who gave him his powers and apparently raised him? They're apparently so creepy that Charlie himself is frightened of them. You know, the same reality warper who just spent the whole episode swaggering about invincibly, smugly confident in his own superiority, and now he's begging the same people he was just bullying not to let them take him away. Then the way his last plea of "I wanna stay" echoes when they teleport him off the ship...
 * The episode 'The Trouble with Tribbles' is mostly a lighthearted comedy, but the scene at the end where dead tribbles fall on Kirk until he's standing nearly waist-deep in them is very... disturbing. It's the equivalent of opening the door to the attic and being bombarded with dead kittens.
 * Ummm...
 * This may sound a little weird, but Chekov under the effects of the Hate Plague in "Day of the Dove." It wasn't...nightmare-inducing, per se, but seeing the goofy Comic Relief character with a bad accent suddenly start attacking everyone and attempt to RAPE some poor lady while whispering creepy things to her was really... disturbing.
 * Balok in The Corbomite Maneuver. Both as young Clint Howard with that adult voice and the alien dummy he pretended to be were scary. The latter even more so because they put that image at the end of every closing credits: you had to see it if you watched every episode from the second season on!
 * Three words: Khan Noonien Singh. Granted, he would get much worse in the second Star Trek film, but even in his introductory episode, "Space Seed", the man was frightening. During his attempt to take over the Enterprise, he makes it clear to Kirk that he isn't screwing around by locking Kirk, Spock, and Uhura in the bridge and shutting off Life Support there in order to get them and the crew to surrender. When that doesn't work, he forces them to watch each other die, one by one, via suffocation in Sick Bay's decompression chamber.
 * Almost everything about NOMAD from "The Changeling", from its genocidal mission to "sterilize imperfect beings" to sending Spock into a mind meld induced Madness Mantra to wiping Uhura's brain.
 * The Constitution-class ship is kind of bright and cheery with the red doors and uniforms and such, right? Well, when everyone on it is dead or almost dead, the emptiness is kind of creepy, creepy like an Abandoned Hospital. Specifically, the Defiant from TOS: "The Tholian Web" and ENT: "In a Mirror, Darkly" and the Republic from Star Trek 25th Anniversary were messed up real bad. It didn't help that Kirk and his landing party on either ship were stuck there without the ability to transport to the Enterprise -- that's right, no escape route despite being on ships falling apart at the seams. And in the former case, on a ship that is phasing in and out of reality as you know it.
 * It was also a bit bad in "The Mark of Gideon" when Kirk is stuck on an eerily empty Enterprise. Loneliness is a sort of hell, particularly for an extreme extrovert like Kirk. Oh, and hello, right before the first ad break, a bunch of pallid faces fade onto the viewscreen without warning, just staring... (shudder).
 * The agony booth from the episode that introduced the Mirror Universe, not to mention just imagining what life must be like on a day-to-day basis in the mirror universe...
 * Pssh, the agony booth is kids' stuff compared to the Neural Neutralizer from "Dagger of the Mind", which, in all honesty, the Mirror Universe probably has as well. The device was originally intended to cure the mentally psychotic, but one scientist decided to make a few..."minor adjustments". Not only does it inflict as much pain as the agony booth, but the operator can make changes to a patient's personality and memories. In the off-chance someone taps into his or her true self, they are inflicted with intense pain, as shown by poor Dr. Van Gelder. Probably the worst part is when a person is in the chamber with the device at full blast and no operator present...


 * "The Alternative Factor," where the two Lazaruses are doomed to forever fight each other in between the two universes.
 * McCoy's injuries during "The Empath". What's worse is that we don't see exactly what happened to him during that time.
 * Gary Mitchell from "Where No Man Has Gone Before", especially the part where Kirk and Spock are monitoring him reading through the ship's library in minutes flat and he turns and stares at them with his creepy, silver eyes. Then there's his powers, being able to make an oasis in a barren wasteland, and wanting to use said powers to make himself a god.
 * A lot of people consider the scene in "Plato's Step-Children" to be hilarious, what with the Tweedle-Dee and Tweedle-Dum song, tap dancing, self-slapping, and Kirk giving a pony-ride to a very small man in a toga. While it's understandable to see it as funny on the surface, consider for a moment a race of people who can force you to do ANYTHING. ANYTHING. On a whim. And not only that, but they can force you to FEEL anything, too -- they have Spock laughing and crying. Spock himself says it best: they could seriously injure or even kill you just because they wanted to or you made them angry. Without even breaking a sweat, with the power of their minds alone. And these people seem to have no moral compass. At all. Imagine the sheer horror of being forced to humiliate yourself and be caused pain just because someone else was selfish, bored, and could.
 * This means a You Bastard moment for people who did laugh at that episode.
 * Not helped that those assholes (the psychics) more or less make Dr. McCoy watch the whole thing in an attempt to make him stay on the planet as their physician, not long after he saved their leader from dying.
 * "Wolf In The Fold": The idea that a seemingly immortal being had been possessing and killing people for thousands of years just to feed on their fear.

The Next Generation
""Is it also true that you have a limited existence?... you exist, then you cease to exist. You call it... death.""
 * While we're on the subject of anthropomorphic drowning hazards, Armus from the episode "Skin of Evil", though some people consider it to be Narm.
 * The Doomsday Machine mentioned for TOS? Another one shows up in the novel Vendetta. It's bigger, it's faster, it's angry, it's haunted by Yandere ghosts!
 * Although it's generally considered a weaker episode, Data's possession in Masks is pretty frightening. He asks Geordi what it feels like when someone is "losing his mind", then gives a perverse smile and adds, "Masaka is waking!"
 * Nagilum. An immortal, nigh-omnipotent Elder Thing who, in the spirit of scientific inquiry and genuine curiosity, decides to study the phenomenon of death. In order to do so, it rips a great big hole in spacetime, traps the Enterprise therein, and makes with the empiricism. Have we mentioned that it manifests as a giant face floating in the void?
 * If that face in the void image wasn't creepy enough, keep in mind it's Nagilum's idea of A Form You Are Comfortable With.
 * Nagilum's creepiest line is worth mentioning:

""Oh, please.""
 * ...Which immediately leads to a redshirt being killed by a forced heart attack.
 * And let us not forget Picard and Riker calmly and matter of factly deciding to self-destruct the ship with all hands aboard rather then have them be killed one by one by Nagilum. The conversation Picard and his Number 1 have over how long to set the count down to the ship's destruction is chilling. It gets worse when Fridge Horror sets in and we remember that besides the crew, the Enterprise is populated by a couple hundred civilians, many of them children. One can't fault Picard and Riker for wanting to spare their crew from the horrible screaming death we saw the red shirt subjected to, but the way they just give up without really exploring any other options is unnerving.
 * They go to a ship that is the exact double of the Enterprise, only there's nobody aboard at all, and there are strange inhuman screams echoing throughout the ship. Then Riker finds Worf, who is freaking out a little, and they ask each other if they were making the screams. They weren't. Then they find the bridge, and every door leads to one of the other doors on the bridge, so they're stuck and are visibly shaken when they return to Enterprise.
 * Worf pretty much lost his shit on the bridge of the doppelganger ship. "THERE IS ONE BRIDGE. ONE RIKER, ONE BRIDGE GRAAHHH." It might be narmful if it wasn't so scary.
 * The episode "Phantasms", specifically the cellular peptide cake (with mint frosting).
 * The cake was freaky, but much worse is watching Data, aka the Nicest of Nice Guys, calmly stabbing Troi in the shoulder over... and over... and over...
 * The first revealing of Data's head, in a cavern in San Fransisco.
 * Later on, time starts to go screwy and we get a glimpse of the energy-draining ghost things.
 * The Devidians, the race of aliens in question, were picked up for use in one of the "Weekly Episode" story arcs for Star Trek Online recently, in the spirit of Halloween. The Devidians in the actual TV episode are nothing compared to the ones in game - they are in absolutely massive numbers, as opposed to the handful seen on TV, and their base of operations is the poorly-maintained innards of a space station that, until recently, was uninhabited since the days of TOS. It was probably the single creepiest quest ever seen in an MMORPG. Worse still, from that point on, you'll occasionally see the lights flicker in the populated regions of the station, and a ghostly Devidian will run by, apparently unseen by everyone else but you...
 * The Borg. 'Nuff said.
 * The Borg Queen is introduced as a talking, disembodied head and shoulders being lowered down into the rest of her body (shown being assembled in later appearances; apparently, her body's stored in pieces when not needed.) Part of the spine hangs from the head and wiggles around in the air until it's all put into place. The aroused look on her face in the moments after being put back together doesn't help.
 * The Return managed to make the Borg even creepier than we saw in the movies. Vicious assimilated dogs, a giant construction/weapon drone (with a spiderlike "scuttler" that emerged from it), pumping organic parts inside the cube, and a multi-bodied engineered drone (only the first body has a head; when Spock asks what it does, he's told "It feeds the tubes."). If it were actually filmed....Yipes!
 * You think the Borg are bad in their current form? Here is some lovely concept art that shows what they were considering making the Borg look like, with such lovely little details as visible intestines behind transparent plating, mobile, sea anenome-style hair made out of pipes, and razor-sharp sickles attacthed to the Borg Queen's frigging wrists. Creepy does not even begin to cover it.
 * In their introductory episode, a drone beams into main engineering and scans the ship's computer. It takes two phaser blasts to kill it, but is immediately replaced by another drone, and when Worf fires again it's blocked by the Borg shields. The drone then starts seriously messing with the Enterprise systems while staring very creepily at Picard and crew.
 * In Parallels you see a desperate and half-mad Riker begging for help from the alt-uni Enterprise. In his universe, the entire Federation has been overrun by Borg, and he is the only man shown on the bridge. He is so desperate to prevent himself from returning to his own dimension that he tries to kill Worf and by doing so endanger all of the multiverses in the process. Thinking about what the rest of that universe must be like gives me the heebly-jeeblies.
 * Let's not forget Q's behavior when the Borg where first introduced. At first he seemingly sent them into Borg space out of child-like spite. But to just coldly brush off the real deaths of eighteen innocent people as a BLOODY NOSE!


 * It's an unsettling reminder that Q, for all his puckish pranks and amusements, is genuinely a threat on his own, and he is so far above the Federation on the food chain that the lives of a handful of Starfleet officers means absolutely nothing to him.
 * Q in general could be seen as Nightmare Fuel. Though he does have humanity's best interest in mind, for the most part, he is still a jerkish reality-warping alien who will gladly toy with you (mentally and physically) for his own amusement. Not only will he wipe out entire civilizations out of pure boredom, but he can also alter the laws of physics with little-to-no effort. And that's not even getting into how dangerous he can be when he's angry.
 * The Next Generation also had an episode where a child's imaginary friend turned out to be an evil alien. So you have a cute little girl telling another cute little girl that if she won't play her way, she can just stay and die with all the others.
 * Not to mention her creepy expression and line delivery all the way through.
 * Wesley Crusher may be a Creator's Pet, but the doctor's teenage son getting impaled and screaming isn't something you see every day.
 * The first season was quite full of fuel. Watching neck squirm and throb at the end of Conspiracy is still truly squick.
 * After In one version of it, at least.
 * And then after that
 * I feel it's worth noting that said parasite was the saddest sock-puppet alien I'd ever seen. The concept art on the other hand: Looky man looky!
 * Don't forget the time everyone on the ship but Data is slowly transformed into prehistoric animals.
 * And the episode where the ship gets cleaned by an energy field slowly sweeping through it that will kill any living being it touches. Of course, Picard and some thieves get caught on the ship when the field is activated. (One isn't seen dying, but is certainly heard dying, screaming horribly.)
 * One episode had a Red (Gold) Shirt die by getting phased halfway through the floor.
 * The episode where Dr. Crusher gets trapped on a deserted Enterprise in the collapsing universe may be far scarier than was intended. There's a particular kind of hopeless terror when the borders of reality itself are closing in on all sides. The recent New Scientist article predicting that this might be what it would actually look like when the universe ends does not help.
 * People start vanishing and no one except Dr. Crusher believes they were ever there, not even the ship's computer. At least when the pocket universe started collapsing you knew what was going on.
 * The collapsing universe part almost came as a relief. What would have been far worse was if Crusher had just been left there, completely alone on the Enterprise, with everyone she knew gone, no way of possibly running the ship by herself, and still having no idea what happened.
 * COMPUTER: "The universe is a spheroid region 705 meters in diameter." CREEPY.
 * How about that "Out of Phase" episode, where Geordi and Ro, who were trapped in the alternate phase of reality, dealt with a guy by kicking him out into space through a solid wall? Or the creepy incarnate when they appeared at their own funeral as ghosts writhing in pain as the Applied Phlebotinum of the episode revealed them to the rest of the crew?
 * Applying Fridge Logic to this episode makes it even worse. It's established that the people who are out of phase aran't able to interact with matter. This means that the out of phase people don't need air, or else it would have been a very short episode. Given that they don't need air, we can surmise they probably aran't affected by changes in temperature or pressure. Now apply all this to the Romulan who got shoved through the hull of the ship, last seen drifting off into space unable to counter the momentum of the push that sent him through the hull. Instead of dying a relatively quick death from exposure to space, the poor bastard will instead drift through space until he finally dies of dehydration.
 * You're being too generous. He might die if he's lucky. It could be possible that you can't die out of phase, and that he'll just fly through space forever, unable to touch anything or communicate with anyone. And all he really wanted to do was avoid such a fate.
 * It can be even worse than that. Apparently people out of phase are still affected by gravity and can feel pain. Add into this potential immortality and, well, he's going to have to drift by a sun or a star eventually...
 * At one point in the episode "Night Terrors," Dr. Crusher hallucinates that an entire morgue full of sheet-covered bodies are sitting up on their slabs. It's unspeakably unsettling.
 * That whole episode is made of nightmare fuel. Also noteworthy are Counselor Troi's psychadelic visions: Eyes in the dark
 * One of the more subtly creepy moments is when Picard is sitting in his office, and the door chime starts sounding... over and over and over... and you don't know or see what's causing it. Keep in mind, this is before you really start to realize what's going on in the episode, so the fact that no one is activating the door chime is freaky as hell.
 * The entirety of the episode "Schisms," where Enterprise crew are abducted and experimented on while they sleep by creatures from deep subspace. Particularly the scene where the abductees try to reconstruct their nightmares on the holodeck, ending with them standing around a creepy operating table in the dark with strange clicking and buzzing noises in the background. You can even see an abductee's hands climbing toward her face in horror as they get more and more accurate. Or perhaps the scene in sick bay where Riker learns that his arm has been severed and then reattached while he was asleep.
 * Apparently, the aliens from Schisms were never brought back because Brannon Braga didn't find them "terrifying" enough (!) to be worthwhile. I still would have been creeped out had they been giant pink bunnies.
 * What about that serious Mind Screw in Frame of Mind?
 * The episode Identity Crisis, wherein Geordi (along with a few others) contracts a parasite and is transformed into a bizarre alien creature. And that's how that species reproduces...
 * The scene in the holodeck where Geordi is de-constructing the video footage shot on the original away mission, gradually removing all of the crew members that were present until there's one remaining shadow, and nothing causing it: the computer prediction of the shape that cast the shadow is a formless, faceless blob.
 * The "psych test" Wesley undertakes as part of the Star Fleet entrance exam. Everything about the test is terrifying, and it's also notably a rare season 1 instance where the Creator's Pet does not come out on top.
 * "Sub Rosa" has Dr. Crusher seduced by an energy being who claims to be an 800-year old human ghost. It does this by absorbing into her, and she reacts with visible ecstasy. The being ends up taking over her mind and trapping her on his planet, all while claiming to love her and only wanting to make her happy.
 * How about the moment where her grandmother's corpse sits up in its coffin during a lightening storm with demonic, glowing blue eyes!
 * Very fitting, as the script for that episode was based on a story written by Ann Rice.
 * The scene where the ghost first appears behind Beverly in her mirror could induce a heart-attack.
 * In "The Child", Counselor Troi is forcibly impregnated in her sleep by a non-corporeal life form. Enough said...
 * Those... creatures... from "Realm of Fear", those... worm-things, slowly coming into view in the middle of the transporter haze.
 * "The Most Toys" features what's basically a phaser on steroids that boils its victims from the inside out, giving them a few seconds of unimaginable pain before they die. And we actually see a full body shot of someone being killed by it!
 * Lore. When he first appears in "Datalore," he's vaguely creepy. Then you find out that he's a ruthless sociopath, and that's creepier. But it's during the scene when he kicks his deactivated brother in the head, twice, for no practical reason, that he becomes truly terrifying. He isn't merely pragmatically self-centered; he ENJOYS hurting people. And he's strong and fast enough to tear out your femur and stab you with it before you could scream.
 * "Conundrum" presented the incredibly unsettling notion that the crew's mind could be wiped and the entire crew be turned against a technologically inferior civilization without even realizing it. Just the notion itself is Paranoia Fuel.
 * The episode Violations is terrifying enough to watch as a child, but understanding the literal Mind Rape implications of the telepathic attacks pulls it squarely into Adult Fear territory.
 * "The Game", especially when Wesley goes to talk to Picard about starting an investigation. You see him putting something down as Wesley enters, and then after he leaves, Picard turns around and picks up a copy of the game without a word.
 * Dark Page. I first saw it when I was around ten or so, and it scared the hell out of me. If you never thought Lwaxana Troi could be scary... yikes. To make matters worse, it was aired back-to-back with Phantasms which is ANOTHER deeply unsettling episode.
 * TNG never got a Mirror Universe episode, but the book Dark Mirror gives it a go, and it's nasty. Troi as Mind Rapist and Picard as a murderous psychopath were bad enough, but then Good!Picard discovers that this universe perverted William Shakespeare into a twisted parody of the literature we know. He can't even bring himself to look at his antique copy of The Bible (presumably he wants to sleep sometime).

Deep Space Nine

 * The Death of Mirror Universe Odo in "Crossover."
 * Odo's physical decay in "The Die is Cast."
 * Any time Odo is strung out and needs to turn back into his true form to rest, but he can't. The makeup effects are impressively Squick.
 * In an episode in which someone is killing Kira's resistance cellmates, they send her messages saying "That's one", etc. as each person is killed, in a deeply creepy Saw-type distorted voice. Even creepier?
 * In "Field of Fire", when the murderer is revealed, he says he committed his crimes.
 * Another creepy moment happens .''
 * The Reveal that the Changelings had infiltrated the Federation. "It's too late; we're everywhere."
 * While Sisko is dealing with dissension within Starfleet that's led to martial law, a Changeling (in the form of nice, fun O'Brien no less) stops by just to taunt him. "What if I told you that at this moment there are only four Changelings on this planet? And look at the havoc we have wrought."
 * That lovely scene when the Bajoran woman hangs herself on the crowded Promenade.
 * The Dominion has "Houdini" anti-personnel mines, which hide in subspace and make you "disappear" -- at a randomly chosen instance, not by predictable rules. So basically, if you have no way to detect them, nowhere is safe anywhere they've been laid, even places you've passed hundreds of times.

Voyager

 * Show Within a Show version: There's a sequence in a child's holodeck program in which a massive fire monster hops out of nowhere and burns the main character to what looks like death if the kid's not bright enough to figure out how to help him. Worse happens in some children's stories, but the Holodeck is virtual reality -- 3D, immersive, in your face, and by the 24th century, as realistic-looking as reality. The idea of any programmer making such entertainment for a child seriously stretches Willing Suspension of Disbelief.
 * Unintentionally terrifying things in media made for children have been a staple since fiction began.
 * What about the macroviruses? Giant germs that popped out of victims' necks, buzzed around like insects, and eventually grew from bug size to bird size to monstrous.
 * Now imagine how much worse it must have been for Naomi Wildman. Bugs as big as her, and Mommy is sick.
 * Although, watching Janeway wrestle one to the ground and stab it to death is kind of hilarious.
 * Telepathic pitcher plant.
 * And then there's Species 8472, for the Body Horror they can inflict simply by touching you. They scare the Borg as much as Locutus and the Borg Queen scared some of us.
 * It's not what they can do to you -- it's that they can defeat the Borg. And not just defeat the Borg but do it easily. To put this into perspective, whenever a Borg cube appears in Federation space there's usually a dozen or more ships mobilized to fight it and even then there's heavy casualties. At one point an 8472 ship was drifting, unharmed, among a bunch of Borg cubes, lazily taking pot shots at them and blowing each one away with one or two hits.
 * Just remember their introduction. Two Borg cubes float towards the camera and the 'We are the Borg...' speech is heard. BEFORE THEY FINISH, 8472 weapons fire and both cubes go BOOM without a chance to fire a single shot. It's that infamous speech trailing off as the cubes turn into nothing but debris that catapults it into High Octane.
 * Species 8472 were introduced in an episode featuring a small mountain of mutilated Borg corpses. Gah.
 * And later on, they Blow up a Borg planet. If the Alderaan scene is scary, imagine this being done by a couple of Voyager-sized ships, with the beams first converging on a central one before hitting a planet - and instead of clear "Hit and Boom" one sees as the planet disintegrates piece by piece!
 * The creatures the Equinox crew harvested for their advanced warp drive were creepy, and they popped out of portals and as such could attack from anywhere without warning. Complete with monster's-eye view of screaming crewmen as the creatures pounce on their faces. And what they do to you if they get you is at least as bad as Species 8472.
 * It doesn't get worse than the Vidiians, though. Afflicted with a disease that wastes their bodies to the point where most of them make your average zombie look like a GQ model by comparison, they attack ships to harvest crews' organs. Instead of the usual ray guns, their weapons teleport organs right out of victims' bodies. Skin is in demand as well, and many a Red Shirt has been taken away only for a Vidiian to return still looking pretty rotted... except for the face, which now has human skin that doesn't fit very well. And only the face, not the rest of the head, furthering the glued-on-skin look.
 * A particular(ly gruesome) example.
 * "The Thaw" in which members of the crew are trapped in a dream-like computer program where they are held captive by, ridiculed and almost killed by, not a Monster Clown but a whole bloody monster circus. The clown was the ringleader, played by Micheal McKean as a Large Ham. The part that I remember the most is when the whole circus sings out "A VI-RUS! A VI-RUS! HE THINKS WE ARE A VI-RUS!" in a chillingly demented way.
 * "Scientific Method" in which the crew are being experimented upon by invisible (phased) aliens. When Seven of Nine alters her optical whatevers, we see the crew walking around with 'things' sticking out of them while being followed by alien scientists like labrats.
 * And for extra pants-soiling fun, the scene where one of the aliens walks up to Seven and starts adjusting one of the unholy devices attached to her face. And we never get to see what it looks like. And Seven absolutely cannot react to whatever horrors she sees or else she would give the game away to the aliens and they would exterminate Voyager's crew as "failed test subjects".
 * After enough "special moments" like this, the network (or at least the local affiliate in my area) all but started advertising it as a horror show. "Such-and-such happens on The Sentinel, and then Star Trek Voyager unleashes another hour of terror." They're right!
 * Kes screaming in "Persistence of Vision" and "Cold Fire." Major spoilers for the former - one of the best episodes ever - follow.
 * Persistence of Vision gets special points for some of the hallucinations - the Body Horror ones were awful, but perhaps even more so were the more Lotus Eater Machine ones. Just think... a loved one appears to you and even knowing what's going on doesn't keep you safe - all you have to do is listen for about twenty seconds and you wind up trapped, staring into space with God-only-knows what going on inside your head (the episode had some Less Is More going; we don't know what happens to you when you succumb and become basically catatonic and that made it worse somehow.) And then the way it ended...
 * Those hallucinations and creepy whispers in "One", and the pure terror in Seven's voice when the Doctor goes permanently offline.

Enterprise

 * The Xindi Insectoids are enormous computer-animated ants. Industrial Light and Magic gives us all the detail on them you'll ever want and then some.
 * There was also the automated repair station that turned out to kidnap crew members and fake their deaths so it could use their brains in its computers. Archer blows it up in the end... but the final scene is it beginning to put itself back together.
 * Worst of all, though, is the much more graphic portrayal of what happens to victims of Explosive Instrumentation. When the ship gets attacked, other Treks have the Star Trek Shake and the occasional sooty He's Dead, Jim person. Enterprise has things like people on fire and screaming, or crewmen blown out into space when the hull is breached, twitching for a bit, and then stopping.
 * Most of the episode "Strange New World" was creepy, but the worst was when they beamed up the crewman during a storm
 * Singularity seems like a "Naked Time"-ish episode, where everyone is obsessed with tiny tasks and becomes extremely agitated. T'Pol is unaffected, so she goes to check if Doctor Phlox is also all right. He isn't.
 * In Doctor's Orders Phlox experiences hallucinations whilst he and T'Pol are the only member of the crew awake for a trip through radiation that is dangerous to humans. At the end,

The Movies

 * Star Trek the Motion Picture The whole damn, interminable thing! THAT is terrifying!
 * Actually, specific events in this movie are a great example. In this movie more than any other Trek production, every aspect of space travel in the 23rd Century IS TRYING TO KILL YOU! The transporter disintegrates the ship's science officer. Crewmembers make extensive use of space suits for EVA. Going to warp accidentally throws you inside an uncontrollable wormhole. And remember those 300-year old space probes? One of them is coming back, and it's dragging a giant machine thousands of miles long that is more than capable of rendering the planet Earth completely lifeless. What's more, it's been sent by a race of machines that don't even perceive carbon-based organisms as living beings. V'ger is looking for God, and if it doesn't find it, it will nuke your planet.
 * Star Trek II the Wrath of Khan
 * The thought that whatever happened on Omicron Ceti V since Kirk marooned the Botany Bay survivors there was sufficient enough to drive Khan of all people to the point of utter madness is pretty nightmare-inducing. In Space Seed, Khan was himself a case of Nightmare Fuel; in the movie, he's gone completely psychotic.
 * Star Trek III the Search For Spock


 * Star Trek Insurrection. The flesh stretching process of the Son'a. Only somewhat Nightmare Fuel until head baddie Ru'afo
 * Star Trek Generations. When Data's newly-installed emotion chip overloads and he goes Laughing Mad, it's creepy as hell.
 * Star Trek (2009). This movie is surprisingly tame compared to most Star Trek movies, but there are still a few moments:
 * The indistinct voices heard inside the Narada at one point.
 * The Narada is about twenty miles long, hideously overweaponed, and covered in blades and tentacles caused by uncontrollable Borg growths. There is nothing Accidental about the Narada's Nightmare Fuel.
 * Being beamed inside a cooling system.
 * That Eldritch Abomination monster on the ice planet.
 * Then there's the early scene where a crewmember gets sucked out of a hull breach, their screaming silenced when they end up in the vacuum...

New Voyages

 * "Blood and Fire" is about Regulan bloodworms. The ones the Klingons were joking about in "The Trouble with Tribbles". Regulan bloodworms are not funny. Or cute. Or harmless and useful, like the ones in Enterprise. Point of fact,