Batman: The Animated Series/Nightmare Fuel

""It's in me, Batman!""
 * Clayface is certainly a terrifying character already. His introductory episode was bad enough, but there's a follow-up episode that had him creating a little girl out of his substance to act as a "lookout" to see if it was safe for him to come out of hiding. She acquires a self-identity and tries to escape and befriend Robin. Nevertheless Clayface reabsorbs her, to her terror.
 * NOTHING says "Don't Do Drugs" like after Mr. Hagan is forcibly overdosed and left in the backseat of a car in the back alley. He starts to melt.
 * In his second appearance, Clayface trapped Batman within his own body and you can see him struggling within the clay body as he slowly suffocated.
 * "Feat of Clay". It all starts with a man being held down as you see chemicals poured on his face, while he thrashes, screaming. It gets more fun when you see him rip chunks off his face to throw at people, and watch him mutate in all sorts of demonic shapes. Oh the nightmares.
 * In "Mudslide" Clayface pulls Batman inside his body in order to smother him to death. Batman is seen struggling to get out (at one point a clay-covered silhouette is visible), and Clayface spends the whole time describing how his struggles are getting fainter and his heartbeat is growing weaker.
 * Clayface's whole shtick of slowly liquifying to his death could be disturbing enough to qualify as Nightmare Fuel. Especially since it doesn't end well.
 * One word: ManBat.
 * Kirk Langstrom's transformation scene in "On Leather Wings". Mostly because of how well it's animated. It looks like something out of a werewolf movie, and combined with the sound of his laugh degenerating into a hypersonic bat screech, the whole sequence tends to stick in the mind.
 * The scene where Langstrom, creepily calm, explains that he's addicted to the Man Bat formula and then transforms right in front of Bats. The episodes Animation Bump doesn't really make things less nightmarrific.

"Bane: "A fight to the death?" Batman:"
 * There is a followup episode where someone has managed to duplicate the ManBat formula, and all clues point to the reformed Dr. Langstrom. Fridge Horror kicks in as you realize Kirk truly has reformed and is starting to wonder if he is simply unaware of his Enemy Within. Even worse, it turns out the new ManBat is his wife, who had absorbed some of the formula through a wound she had while she helped him destroy the formula. That ep launched Kirk straight into Woobie territory.
 * Anything to do with Scarecrow. (Except for the episode that introduced him, which had bad animation and gave him a very un-creepy booming voice.) As befitting his name, he is Nightmare Fuel incarnate, exposing people to their greatest fears which end up terrifying the audience as well. His image-upgrade in The New Adventures of Batman from a skinny dude with a stupid mask to a corpse with a rope around its neck certainly doesn't help matters. Nor did getting Jeffrey Combs to do the voicework.
 * "Never Fear". When Bats discovers Scarecrow is giving people chemicals that makes them dangerously fearless (the opposite of his usual MO), he starts snooping and gets himself captured. He excuses his actions by pretending to be a common thief - which doesn't stop Scarecrow from giving him a dose of the stuff, causing him to jump into the water with a mess of crocodiles. They pounce, he goes under, and we see a huge cloud of blood swirling up through the water as Scarecrow walks away smugly... Guess who was actually bleeding, though.
 * The scene in the Scarecrow's first episode, when he gasses the dean of Gotham University, who then looks at his hands and sees nothing but their bone structure.
 * "Dreams in Darkness". Batman's nightmares. The first one involved the death of his parents and it ended with a giant gun pointing at Batman as he was surrounded by flames. In the second one, the Joker appears and turns into another villain, who then turns into another villain and so on (Joker -> Penguin -> Two-Face -> Ivy). Batman then gets pulled into an abyss where he's devoured by a giant Scarecrow. The worst thing is that in the second dream, both Robin and Alfred watch the whole thing while saying that it's for his best.
 * The Scarecrow is unnerving at best, but there's one particular shot of him in the episode "Fear of Victory" that looks like all your childhood nightmares diluted into one look.
 * The Scarecrow himself was actually kind of cartoony during his first incarnation in TAS, but his redesign when it became part of The New Batman/Superman Adventures is bonechilling. The fact he's voiced by Jeffrey "Dr. Herbert West" Combs, that just goes beyond the pale.
 * The episode "House and Garden" features Poison Ivy with a husband a kids that turn out to be plant-based clones she created. We find this out when several pods in her basement hatch babies, who, while calling for "Mommy" grow into hideous monsters in a few seconds. Sadly, this was closest Pamela could get to being normal. No wonder she got so bitter later on. (See below)
 * They top this with a later episode, "Chemistry," in which a man is revealed to be one of Ivy's creations when she rips off his skin. Later, Robin sprays the plant-guy with defoliant, which causes him to melt slowly and graphically, including his eyeballs falling out and floating off. Bruce's new wife turns out to be another plant-person when her legs turn into vines... and the last we see of her is her face staring out of the porthole of a sinking ship as Batman flies away.
 * Crossing into Uncanny Valley was the episode House and Garden when Poison Ivy creates children out of plants. First, Batman and Robin end up in her basement, saving her "husband" who was in a huge vat of water, and then they hear children saying, "Mommy...mommy," they turn, and see children coming out of the plants. It's hard to explain on the page, but holy crap that was scary...
 * Ra's al Ghul's Psychotic reaction after being put into the Lazarus pit, and nearly throwing his own daughter into the pit!
 * The end of "Showdown". In this episode, Ra's Al Ghul and his League of Assassins kidnap a resident from a Gotham rest home, and leave a tape for Batman, on which Ra's Al Ghul relates a story about how in 1883, his plan to take over America was thwarted by none other than Jonah Hex, who was seeking to claim the reward for Ra's' lieutenant, Arkady Duvall. In the end, Hex captures Duvall and turns him over to the authorities. After this story concludes, Batman and Robin catch up with Ra's and his still-unknown captive...
 * "See No Evil". A psychotic man used an invisibility suit to secretly trick his daughter to leave with him. The man in question was - it's not just scary, it's a Tear Jerker.
 * In "Wolf's Moon" the thought of Romulus presumed to be trapped as a mindless Wolf Man because he was ''prevented from getting the antidote because Professor Milo dropped the antidote when werewolf-Romulus got all snarly at him.
 * The Mad Hatter starts out as a sympathetic loser, but by the end of the episode in which he is introduces, he gains a creepy stalkercrush and the ability to turn anyone into a mindless puppet. And Alice winds up in a different outfit than she started with...
 * The episode with the Sewer King and his underground child slaves. Thankfully, Batman took him down; in fact, Batman was so enraged that he was trying to prevent himself from crippling the guy on the spot - or worse - and made the Sewer King acutely aware of that.
 * What happens when Bane gets a little too much venom.
 * A bit more subtle, but how about the poor guy who inadvertently insulted Joker for cutting him off in traffic? He kept changing his name and moving, but the Joker never lost him, blackmailing him to do his dirty work.
 * In particular, the moment when the guy is yelling at him in traffic and the Joker slowly turns and just grins at him, followed by the calm, easy way the Joker starts following him is the stuff of nightmares.
 * The plight of the poor schmuck the Joker terrorizes in this episode is almost Kafka-esque in how surreally terrifying it is. Imagine driving home one day only to get into a random road rage incident with the most infamous, dangerous and readily identifiable psychopath quite possibly on the entire planet. That's the kind of misfortune that could get you to thinking the universe is out to get you...
 * The poor schmuck who thought he killed Batman was thrown into a coffin by the Joker and being lowered into a vat of acid.
 * Anything with Joker is prime nightmare fuel, from disguising himself as a harmless party magician so he can kidnap the mayor's son to the creepy, horrid smiles his victims wear.
 * Especially the first time they show the effects of Joker Venom in The Laughing Fish. Not only does the poor guy have what's best described as a laughter induced seizure, but his eyes bug out to about twice their normal size and his mouth twists into a horribly wide rictus as the unwilling laughter gets more and more terrifying.
 * The more you think about it, the more Paranoia Fuel this situation generates. To give a bit of background: The Joker attacked the guy in the first place because he explained that Joker's Joker Venom-afflicted fish (Nightmare Fuel in their own right) couldn't secure a copyright. Such logic works on Joker as well as you think it would. The guy even explained to Batman that it wasn't even his fault that Joker couldn't get a copyright; he was an ordinary pencil pusher. And Joker still comes after him. In the words of the comic that the episode was adapted from: fail to conform to The Joker's mad logic, and you've just dug your own grave.
 * It gets worse. The Joker had Harley spray Francis with the first part of the gas before Francis actually refused Joker's request for a copyright. The Joker KNEW he couldn't get a copyright for the fish, and he just wanted to kill off the pencil-pushers anyway.
 * In "Batman: Mask Of The Phantasm", A man DIES OF LAUGHTER!!!
 * In Mask of the Phantasm,.
 * "Beware, The Creeper" is mostly funny, but the scene where the Joker has attacked Jack Ryder with the Joker Venom, causing him to fall helplessly to his knees while pleading "help me!" in between horrible forced laughter is terrifying.
 * As mentioned above, the Joker goes to the mayor's house disguised as a party clown. However, he doesn't go to kidnap the mayor's son. His original intent was to blow the garden up with dynamite, along with the mayor's social circle and the children attending his son's birthday party.
 * And then there's the time he had a creepy robot clown driving his boat that emitted a cloud of laughing gas all over Gotham. It seemed pretty innocent until it was established tat lengthy exposure to said gas would result in untreatable insanity. Which really hits home when we see Alfred—Bruce's surrogate father—afflicted by the gas.
 * The Hand of Fate in Riddler's introductory episode was inexplicably frightening.
 * A giant disembodied hand that will randomly whisk you off into the sky if you make the slightest mistake? While you're on a sadistically short time limit? To a kid who's watching this? Yeah. Freaky.
 * Batgirl's dream sequence death was particularly traumatizing, as she falls from a high rise, onto her fathers car. made even worse by a censorship edit that put the camera inside the car with Jim Gordon as his daughter hits his hood.
 * Batman's implied change of policy in this episode.

""How do you plead?" "Guilty... guilty... guilty...""
 * "Avatar". The immortal Egyptian queen, who at first looks beautiful to Ra's, then turns out to actually look... well, like a bazillion-year-old mummy woman should.
 * Two-face. He starts off seeming like a normal nice guy, then his second personality takes over and he spends the rest of the series chaotically basing his every decision on coin flips. Then there's the burn scars, which are somehow a thousand times scarier because they aren't realistic. They took artistic liberties and made them sky blue, swelled up his lips on one side and made them hang open, and gave him that freakishly enlarged, yellow, blind eye.
 * When Harvey Dent saw what happened to his face. His poor girlfriend wasn't the only one who screamed.
 * The ending of Judgement Day, as it ends with Harvey in his prison cell, playing out a trial in his own mind:


 * In the origin episode of Two-Face, Rupert Thorn is trying to blackmail Harvey Dent (with the information of his split personality, pre-accident) into looking the other way, and offers him a trade. Harvey is getting visibly more and more pissed as Thorn details the trade, and then suddenly goes completely calm. "Sounds good, Thorn. There's just one problem." and then his face turns to sadistic evil incarnate and in his creepy, psychotic criminal Two Face voice says "You're dealing with the wrong Harv." and proceeds to kick the crap out of Thorn and his goons. It's not nightmare fuel due to gore or torture, but the sudden conversion from Harvey Dent to "Big Bad Harv", and the lighting and way his face contorts, is 100% pure grade A nightmare fuel to younger viewers.
 * When he had the plastic surgery to get his face repaired. He rips half of his face off in that episode.
 * In "The Demon Within", Jason Blood says that Klarion turned his parents into mice, and then we get a close-up on his snarling pet cat. Nothing is stated outright; the audience are left to draw their own conclusions.
 * A brief segment of "Moon of the Werewolf", ending with the mad scientist threatening the guy with, "If you want the antidote, you're going to do everything I say."
 * ...One shouldn't watch Mask of the Phantasm and Return of the Joker together. For the first time. Right before bed. You'll have nightmares about being stalked and chased by the Joker.
 * Such is the power of B:TAS's Nightmare Fuel that it extends to the damn activity center based off of it. Never mind the creepy ambiance. Never mind that all the games set in Gotham pit you against such pleasant fellows as Two-Face and the Joker (the game set in the sewers implies that Killer Croc is there, making it even worse). Never mind that all that can be heard in Wayne Manor is that damn clock. If you try to continue a game, you'll first have to confirm whether or not actually continue it or start a new game--on a blood-red screen of the Joker staring right at you, taunting you with the knowledge that whichever choice you make, you'll never catch him. Oh, and every time you exit back to Gotham, he laughs at you from off-screen. (There's apparently another edutainment B:TAS game wherein, if the cover art is anything to go off of, you have to stop the Joker from murdering Robin. It's probably even worse.)