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* ''WesternAnimation/AdventureTime'': The Christmas episode shows that, centuries ago, before TheEndOfTheWorldAsWeKnowIt, this happened to an antique collector by the name of Simon Petrikov after he made the mistake of wearing a cursed artifact. A thousand years of sanity slippage later, the man he was is completely gone, and what remains only knows himself as [[spoiler:the Ice King]]. Later episodes document Simon's attempts at surviving and [[spoiler: raising Marceline]] after the nuclear holocaust, and his desperation at remaining himself. Being harassed 24/7 by the spirits in his castle (that only he can see, thanks to his wizard eyes) probably hasn't helped any, either.
* ''WesternAnimation/AmericanDad'':
** One episode has Stan going insane when [[CantTakeCriticism his neighbors criticize him]].
--->'''Hayley:''' He's right, Dad. You're going insane.\\
'''Stan:''' Oh am I!? Would an insane man try to ''drink you?! (holds up Klaus' bowl to his lips and starts drinking the water)''
** Francine undergoes some in "Stan of Arabia" after being forced to become a subservient wife under Arabic laws, culminating in her breaking into a musical number about how Saudi Arabia is the worst place in the world while dancing nearly nude and breaking as many laws, norms and taboos as she can.
* ''WesternAnimation/{{Animaniacs}}'':
** This happens almost OncePerEpisode to the unfortunate soul the Warners decide to be their "special friend". Most of the time [[AssholeVictim they deserve it]], though.
** On a rare occasion, the Warners themselves, who usually [[ObfuscatingInsanity feign insanity]], will ''genuinely'' go insane when even they can't cope with the madness.
** Slappy Squirrel suffers this in "One Flew Over the Cuckoo Clock" after being forced to watch talk shows.
** Candie the Chipmunk gets one in "I Got Yer Can" after Slappy takes revenge on her for telling Slappy to take her soda can out of Candie's trash can.
* ''WesternAnimation/{{Arcane}}'': As Viktor is being wracked by illness and Jayce is led astray by the council's politics, he becomes worryingly obsessed with his work, [[spoiler:and after learning he will die of his illness soon, implicitly over how Hextech could prolong life]]. After becoming disillusioned enough with Heimerdinger's resistance to progress that could [[spoiler:save his and others' lives, he goes off to find Singed again and acknowledges that his extreme means to sustain life are ultimately right. He willingly takes [[PsychoSerum Shimmer]] and essentially performs BloodMagic all in an attempt to survive.]]
* ''WesternAnimation/AvatarTheLastAirbender'':
** Aang goes through one due to sleep deprivation. He starts out with just encouraging everyone to prepare for alarmingly specific things to go wrong and ends up having a several-minute hallucination of a swordfight between Momo and Appa while a six-armed Guru Pathik floats past singing about chakras.
** Azula in the finale. Her slippage began with [[spoiler:Mai and Ty Lee's [[HeelFaceTurn betrayals]] a couple episodes]] earlier. When Ozai told her to remain in the Fire Nation as Fire Lord, she became increasingly more [[TheParanoiac paranoid]]. She acted on the paranoia, then began hallucinating, and eventually had a VillainousBreakdown.
%%* ''WesternAnimation/BatmanTheAnimatedSeries'': Harleen Quinzel, who would later become Harley Quinn, in "Mad Love".
* ''WesternAnimation/BobsBurgers'':
** "[[Recap/BobsBurgersS1E2CrawlSpace Crawl Space]]": Bob suffers this whilst he is stuck in the wall, and even talks to Louise's nightlight Kuchi Kopi and is convinced it's alive.
** "[[Recap/BobsBurgersS1E7BedAndBreakfast Bed and Breakfast]]": Linda becomes increasingly unhinged as she becomes desperate to prove she's a good hostess.
** "[[Recap/BobsBurgersS3E1EarsyRider Ear-sy Rider]]": Louise [[CloudCuckoolander was never exactly the sanest kid around]], but in this episode she has a mental breakdown after her bunny ears are stolen. [[spoiler:It gets even worse when she thinks they've been destroyed.]]
** "[[Recap/BobsBurgersS4E18Ambergris Ambergris]]": Louise has another as [[GoldFever she tries to find a way to profit off the highly expensive ambergris]].
%%** Felix Fischoeder is not too sane, but suffers this in "[[Recap/BobsBurgersS4E21WharfHorse Wharf Horse]]" and "[[Recap/BobsBurgersS4E22WorldWharfIITheWharfening World Wharf II: The Wharfening]]".
* ''WesternAnimation/CatDog'': Happens to Dog in one episode, when he learns that meat comes from animals and becomes convinced that food are his friends.
* ''WesternAnimation/{{Centaurworld}}'': Played for laughs in "[[Recap/CentaurworldS1E7JohnnyTeatimesBeBestCompetitionAQuestForTheSash Johnny Teatime's Be Best Competition: A Quest for the Sash]]", where Zulius becomes increasingly unhinged and haggard looking the moment he enters the Cattaur valley. He goes from wearing an undershirt with hair loops and a perma stubble to looking like a maniac with a blue dress, unshaven hair and a thick beard. He instantly reverts to normal after Horse decides to attend the competition.
%%* ''WesternAnimation/{{Clarence}}'': Jeff in "Average Jeff".
* ''WesternAnimation/CowAndChicken'': While the Red Guy isn't exactly sane to begin with, he ends up having a complete mental breakdown in the episode "I Scream, Man" as a result of taking a job that he despises: as an ice cream man. Predictably, he ends up in a mental clinic.
-->'''Red''': AAAAAHHHH!!!!! I CAN'T TAKE IT ANYMORE!!!! I don't have any ice cream! None whatso...EVER! ''(hangs near the side of the cop, then switches to a calm, quiet voice)'' I don't even like ice cream, ''(switches back to LargeHam mode)'' OR KIDS! It says "Eye Screem" on my truck, not "Ice Cream"! Get it? 'cause I SCREAM!!! Look at me. ''(spins around)'' AAAAAAAAAAAAAAAHHHH!!!!!!!! ''(dizzy)'' Ooh, ha ha. Screaming is my HOBBYYYYYY!!!!!!\\
'''Policeman''': ''(hits Red with a weenie)'' It's the padded cell for you, scream man!
* ''WesternAnimation/DangerMouse'': Isombard Sinclair, the narrator, gets so carried away with his narrative in "Once Upon a Timeslip" that he is removed from the cartoon for a much needed rest. He also loses his marbles at the end of "Tower of Terror."
* ''WesternAnimation/DuckTales2017'':
** "[[Recap/DuckTales2017S2E10The87CentSolution The 87 Cent Solution!]]": This happens to Scrooge after someone breaks into the Money Bin and steals eighty-seven cents, and he goes on a mad search for the thief made worse from being in a bad shape due to a cold [[spoiler:and Glomgold (the culprit) messing with him with a time-stopping device]].
** "[[Recap/Ducktales2017S2E16TheDuckKnightReturns The Duck Knight Returns!]]": Jim Starling learns that someone is taking over his role in a WesternAnimation/DarkwingDuck reboot movie, making it DarkerAndEdgier. Highly upset and unhinged, he attempts to murder his replacement, take over the movie and even burn down the studio. In the end, his mind becomes so deranged that he decides that if they want a grim and gritty Darkwing, they'll get one [[spoiler:becoming ''[[CanonCharacterAllAlong Negaduck]]'']]. Oh, and that replacement? [[spoiler:Oh, [[CanonCharacterAllAlong some nobody named Drake Mallard]] that Launchpad convinces to become the ''real'' Darkwing Duck.]]
** "[[Recap/DuckTales2017S3E12LetsGetDangerous Let's Get Dangerous]]": Taurus Bulba Seems to gradually go crazier and crazier throughout the episode, especially after getting hit in the head by the Ramrod, what with his frequent EvilLaugh, refusing to listen to common sense, turning on F.O.W.L. after Bradford calls him out on his crazy plan and his insistence that he will change the world with his plan in the end despite the fact he is told that [[spoiler:it will destroy everything, as well as summoning a bunch of supervillains just so he can beat Darkwing Duck]].
* Happens all the time in ''WesternAnimation/EdEddNEddy'':
** Eddy loses it on a few occasions, such as in "Laugh Ed Laugh" when everyone but the Eds gets chicken pox, leaving him with no one to scam.
** "Little Ed Blue" has Ed become massively pissed off for apparently no reason. [[spoiler: Turns out [[RampageFromANail he had a pebble in his shoe]]. This revelation drove Eddy crazy too.]] But when Eddy slaps him in an attempt to snap him out of it, Ed goes into a unstoppable rampage, eating metal slides and nearly snapping [[CompanionCube Plank]] in half.
** Kevin starts going manic from paranoia when the Eds go missing in "See No Ed".
** Rolf goes ballistic in "No Speak Da Ed" when a series of wolf-themed gifts from Ed's penpal make him thinks Ed has affiliated himself with a clan of sheep rustlers from the Old Country.
** Edd goes insane in "Cleanliness Is Next to Ed-ness" from not being able to take a shower after he discovers his parents are renovating the bathroom.
* ''WesternAnimation/{{Futurama}}'':
** Fry suffers this in "[[Recap/FuturamaS3E11InsaneInTheMainframe Insane in the Mainframe]]" as a result of being a human confined to a robot asylum.
** In "[[Recap/FuturamaS6E15MobiusDick Mobius Dick]]", Leela goes insane when she [[MobySchtick becomes obsessed with trying to kill a space whale in revenge]].
--->'''Amy:''' You've gone from crazy like a fox to crazy like Fox News.
** Richard Nixon's head-in-a-jar noted he's become "bitter, and let's face it, ''crazy'' over the years" from being stuck as a head in a jar for a long time.
* ''WesternAnimation/GravityFalls'':
** If you look closely at some of the text in Journal 3, it seems like the Author underwent something like this. [[spoiler:He did indeed, as a result of being manipulated by Bill Cipher into building a device that would destroy the world. However, his case was relatively mild, and he managed to pull himself back together -- probably a result of his trip to another dimension.]]
** Mabel slowly starts losing it in the season 1 episode "[[Recap/GravityFallsS1E9TheTimeTravelersPig The Time Traveler's Pig]]" [[spoiler:after Dipper's time travel antics cause her to lose her pet pig]]. After handing out calculators to people across eight centuries, she eventually breaks completely and starts banging her head against a post and doesn't stop for a month, during which time she grows vines and gets a shoulder snail. [[spoiler:Fortunately, it's temporary, and getting her pig back seems to resolve all the problems, but this example is played more for drama than laughs, despite its absurdity.]]
** Old Man [=McGucket=] [[spoiler:[[Recap/GravityFallsS2E12ATaleOfTwoStans helped build the machine in Stan's basement thirty years ago]], but an accident with the device heavily traumatized him. He then built a gun that would [[LaserGuidedAmnesia erase the memory from his mind]], creating [[Recap/GravityFallsS2E7SocietyOfTheBlindEye the Society of the Blind Eye]] so that others wouldn't be freaked out or traumatized by the weirdness of Gravity Falls. However, repeated use of the memory wipe took a toll on [=McGucket's=] sanity, until he was reduced to the junkyard dwelling town kook he is today. It's also implied that he never totally forgot the event that he originally tried to forget in the first place, as evidenced by him making a symbol representing [[BigBad Bill Cipher]], which aided in his fall]].
* Dib of ''WesternAnimation/InvaderZim'' isn't that stable to begin with (being one of the handful of reasonably intelligent people in a CrapsackWorld [[SurroundedByIdiots full of idiots]] will do that), but over the course of the series becomes increasingly desperate, paranoid, and manic, and [[TalkingToThemself talks to himself]] with greater frequency.
* Though Justin Hammer already was a RichInDollarsPoorInSense PsychopathicManchild from the start in ''WesternAnimation/IronManArmoredAdventures'', he gradually loses the little sanity he has left over the course of the series.
* PlayedForLaughs on ''WesternAnimation/JimmyTwoShoes'', when Jimmy is left the only person in Miseryville awake while everyone else is in hibernation. He slowly begins to go crazy.
* The eponymous character of ''WesternAnimation/{{Kaeloo}}'' has lost her sanity several times, most notably in [[spoiler: Episode 100]], but because of NegativeContinuity (except in the aforementioned episode) she is back to normal by the next episode.
* Hank's barber Jack in ''WesternAnimation/KingOfTheHill'' started going senile, culminating in Bill mentioning something about Jack getting in a high speed police chase. Earlier we'd seen him saying he couldn't give Hank a haircut because he didn't have a stapler, spraying Hank's hair with peroxide before walking out of his shop and assaulting someone for their bicycle, and finally dumping shaving cream on his head and removing it with a hair dryer.
** This is oddly reversed a few seasons later when Luanne starts working at Jack's shop and he's got all his cognitive abilities working in okay condition, implying the above was either a nervous breakdown, he'd been put on very strong medication, or bad writing.
** In the episode "Pretty, Pretty Dresses" Bill is very lonely and depressed, and finally loses it when Hank destroys the gifts he'd been saving for his ex-wife Lenore in case she ever came back. He starts wearing her old clothes she'd left behind and talks in a falsetto voice, believing that he himself is Lenore; eventually Hank is able to break him out of it and gets him to get over Lenore.
* ''WesternAnimation/LetsGoLuna'': In "C'est La Vie a Paris", Luna tries to get [[{{Workaholic}} Mr. Hockbar]] to relax. But he somehow finds even ''more'' [[BusmansHoliday work to do]] on what is supposed to be a leisurely day in Paris. This drives Luna insane. She even gets a TwitchyEye.
* ''WesternAnimation/TheLionGuard'': Kion begins to go insane in Season 3 thanks to Ushari biting him in the Season 3, and the aim is to get Kion cured, before he goes insane permanently.
* In ''WesternAnimation/TheLionKingOneAndAHalf'', during a scene approximately taking place during Scar's VillainSong in the original movie, Timon is on the verge of cracking in his "dream home" quest...
-->'''Timon:''' ''(comes across a steam vent)'' Hey! This is home sweet home, baby! Home-- ''(gets sent into the air a bit by the eruption)'' Ha ha! Steam! Ha ha! Steam is good. Steam is--is--is water. Whoo! Gotta have water. You know, for the dream home. Steam home, dream home! Steam, steam, steam.
* ''WesternAnimation/LooneyTunes'': WesternAnimation/DaffyDuck seems to fall victim to this a lot. A perfect example occurs in ''Duck! Rabbit! Duck!'' after he gets shot by WesternAnimation/ElmerFudd one too many times:
-->'''Daffy:''' ''(hysterical)'' Shoot me again! I enjoy it! I love the smell of burnt feathers! And gunpowder! And cordite! I'm an elk -- shoot me! Go on, it's elk season! I'm a fiddler crab -- why don't you shoot me?! It's fiddler crab season!
** Happy Rabbit (the beta WesternAnimation/BugsBunny) in "Hare-Um Scare-Um" does a song that tells how watching Looney Tunes cartoons drove him insane. Imitating a police officer, his throwing the book at John Sourpuss' dog tells all.
--->You know what this'll cost you? Thirty days...hath September, April, June and Montana! All the rest have cold weather! Except in the summer, which isn't often!
** A year earlier, Daffy himself tells how he did quite well working on a merry-go-round until it broke down.
** In ''WesternAnimation/PorkyInEgypt'', WesternAnimation/{{Porky|Pig}}'s camel succumbs to "desert madness" and has a FreakOut that alternates between hilarious and genuinely unnerving.
** In ''WesternAnimation/TheLooneyTunesShow'' not only Daffy, but everybody is liable to get bonkers (after all, it's a mostly CrapsaccharineWorld/ StepfordSuburbia full of {{Cloudcuckoolander}}s). As an example, Porky has turned from an apparently wealthy JerkJock in high school to a middle-class burn-out prone to suffer this [[spoiler:so frequently that it gets in BlackComedy territory]]; and Bugs didn't act like himself after he started consuming "Spargle" (being PlayedForLaughs).
* Often PlayedForLaughs in the new [[WesternAnimation/MickeyMouse2013 Mickey Mouse shorts]], such as "New York Weenie" and "Dog Show".
* Anthony Ivo of ''WesternAnimation/MyAdventuresWithSuperman'' gradually descends into madness from prolonged use of [[TheCorruption the Parasite armor]]. In his first appearance, he's a [[PointyHairedBoss hard to work with]] CorruptCorporateExecutive, but he's still a legitimate genius. However, the armor's horrific effects on his [[BodyHorror body]] and mind cause him to mentally degrade into a raging berserker over time, and eventually is reduced to a borderline feral monster.
* This happens often enough in ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' that its fans came up with the term "Cutie Mark Failure Insanity Syndrome" -- a pony failing to live up to their special talent (symbolized by their cutie mark) -- to describe the most common cause of ponies going nuts. (It's worth pointing out that in all of these cases, the insanity was cleared up by the end of the episode with ThePowerOfFriendship.)%% NOTE TO EDITORS: Please leave the mention of the fandom term for searchability.
** In [[Recap/MyLittlePonyFriendshipIsMagicS1E25PartyOfOne "Party of One"]], [[GenkiGirl Pinkie Pie]] thinks her friends are avoiding her because they're sick of her parties. Her normally curly hair goes straight, she [[CompanionCube makes her own party guests]] out of things like a sack of flour and a pile of rocks (whom she holds conversations with), her colourful persona becomes noticeably darker, as if it's under a shadow, and the normally insufferably cheerful pony becomes cranky, miserable, and borderline paranoid schizophrenic, all the while sporting a SlasherSmile. Her slippage even comes complete with {{Creepy Circus|Music}} [[https://www.youtube.com/watch?v=_cy9gNE_vIE Music]] (which has a disturbing resemblance to the {{leitmotif}} of a certain personification of chaos).
** In [[Recap/MyLittlePonyFriendshipIsMagicS1E26TheBestNightEver "The Best Night Ever"]], [[ShrinkingViolet Fluttershy]] snaps at the Grand Galloping Gala due to all of the animals running in fear from her. After her increasingly desperate methods fail, she goes into full blown {{Yandere}} mode, unleashing animal-based chaos with the line [[https://www.youtube.com/watch?v=rwp60eYuie0 "You're... going to LOVE MEEEE!"]].
** In [[Recap/MyLittlePonyFriendshipIsMagicS2E1TheReturnOfHarmonyPart1 "The Return Of Harmony Part 1"]] and [[Recap/MyLittlePonyFriendshipIsMagicS2E2TheReturnOfHarmonyPart2 "Part 2"]], the [[CorruptTheCutie discorded mane ponies']] misbehavior becomes worse as the episode progresses.
** Twilight Sparkle goes through a complete breakdown in [[Recap/MyLittlePonyFriendshipIsMagicS2E3LessonZero "Lesson Zero"]]. Convinced that she's about to fail her duty to Princess Celestia, [[MadnessMakeover her mane goes disheveled, her teeth grind, her eyes become unfocused]], she [[TalkingToThemself talks to herself]], and she starts [[TeleportSpam teleporting at random]] while undergoing a complete nervous breakdown. It culminates in an (unintended) mass hypnosis of Ponyville that requires the Princess herself to intervene, disappointed at her student for abusing her powers.
*** Keep in mind that all those examples happened in ''five consecutive episodes''.
** In [[Recap/MyLittlePonyFriendshipIsMagicS2E19PuttingYourHoofDown "Putting Your Hoof Down"]], Fluttershy's takes some [[TeachHimAnger assertiveness training]] which [[GoneHorriblyRight works a little too well]], resulting in her [[TookALevelInJerkass taking multiple levels in Jerkass]] and becoming increasingly violent, paranoid and aggressive to the point that she reduces Pinkie and Rarity to ''tears''.
** Twilight goes crazy again in [[Recap/MyLittlePonyFriendshipIsMagicS2E20ItsAboutTime "It's About Time"]] due to a warning from her future self that got cut off before the important bit could be delivered, leading to a spiral down into the depths of paranoia.
** Princess Luna experiences this a thousand years before the time of the series. Literally consumed with [[GreenEyedMonster jealousy and anger]] towards the ponies rejecting [[TheSacredDarkness her beautiful night]] in favour of Celestia's day, she [[FaceHeelTurn transforms into]] [[SuperpoweredEvilSide Nightmare Moon]] and tries to enact [[TheNightThatNeverEnds eternal night]] in a stubborn attempt to ''force'' the ponies to love her, showing that even a [[PhysicalGod Physical Goddess]] isn't immune to CMFIS. In "[[Recap/MyLittlePonyFriendshipIsMagicS2E4LunaEclipsed Luna Eclipsed]]" she runs the risk of having to bear these insecurities all over again when the ponies begin to reject her once more, but fortunately Twilight is there to help.
** Before [[Recap/MyLittlePonyFriendshipIsMagicS3E12GamesPoniesPlay "Games Ponies Play"]] aired, people were expecting another "Twilight goes crazy" episode. They were likely surprised when this trope was {{averted|Trope}} for that episode because Cadance taught her a controlled breathing exercise to relieve stress.
*** But if her hyperventilating near the climax of the episode is anything to judge by, it was a pretty near miss.
** Rarity suffers from this in [[Recap/MyLittlePonyFriendshipIsMagicS4E13SimpleWays "Simple Ways"]] after [[SwappedRoles swapping roles]] with Applejack, and has a complete breakdown in the BadFuture NightmareSequence from "For Whom The Sweetie Belle Toils".
** In "[[Recap/MyLittlePonyFriendshipIsMagicS4E23InspirationManifestation Inspiration Manifestation]]", the more Rarity uses [[TomeOfEldritchLore the eponymous book]]'s power, [[WithGreatPowerComesGreatInsanity the more deranged she becomes.]]
** Rainbow Dash's turn comes in "[[Recap/MyLittlePonyFriendshipIsMagicS5E5TanksForTheMemories Tanks For The Memories]]", where her anxiety at having her beloved tortoise hibernate for the winter drives her to try and ''stop winter from happening''.
** The episode "[[Recap/MyLittlePonyFriendshipIsMagicS7E10ARoyalProblem A Royal Problem]]" shows us that not even ''Celestia herself'' is immune to this. After Starlight switches her magic with Luna's Celestia takes over her sister's nightly duty and expected them to be easier, only to quickly find out that because it's nighttime all the ponies in Equestria are asleep, which leaves her without company. She quickly start talking to herself. A lot. Luna admits to talking to herself as well.
** Queen Chrysalis goes through this in "[[Recap/MyLittlePonyFriendshipIsMagicS8E13TheMean6 The Mean 6]]" after being dethroned as Queen of the Changelings for many months and having to live in the Everfree Forest. When she tries to make evil doubles of the Mane 6 through some trees, she speaks to them as if they were alive.
** As a matter of fact, just about everypony in the mane cast has danced on the further edges of sanity at least once in the series if this [[http://whybronies.files.wordpress.com/2011/07/11389-applejack-demotivational-fluttershy-pinkie_pie-rainbow_dash-rarity-twilight_sparkle.png demotivational poster]] is any indication.
* Kowalski gets this ''a lot'' in ''WesternAnimation/ThePenguinsOfMadagascar''.
* Candace from ''WesternAnimation/PhineasAndFerb''. It's not gradual and it's not regular like most examples, but it's definitely there. Seriously, this girl needs help. She has a psychological need to bust, it's shown at least twice that she can't go without it. That doesn't smack of good mental health... If it wasn't clear before, the episode "Monster From ID", which takes place largely in Candace's subconsciousness, seals it. Candace's head is one messed-up place.
* ''WesternAnimation/PinkyAndTheBrain'': Snowball in "Welcome to the Jungle", where he's the leader of a makeshift jungle tribe made up of tourists and it's implied he's been hallucinating.
* ''WesternAnimation/ThePowerpuffGirls1998'':
** Bubbles has one in "Bubblevicious" as she tries to prove to everyone that she is "hard-core".
** Bubbles suffers this again in "Octi Gone" when she believes that somebody at the party she's at stole Octi.
** Buttercup slowly goes insane in "Moral Decay" while stealing villains' teeth for money.
** Whimsical Willy in "Neighbor Hood".
** Mayor in "Hot Air Buffoon" when trying to save the town goes to his head.
** Dick Hardly from "Knock It Off" becomes gradually more unhinged as his fortunes (and greed) grow.
** Mojo Jojo in "You Snooze You Lose" ''totally'' flips out when he sees the Amoeba Boys have somehow built and assembled the device he designed to get rid of the Powerpuff Girls once and for all, and accidentally tricked the girls into getting into it.
* ''WesternAnimation/ThePowerpuffGirls2016'':
** Bubbles has one in the episode "Bubbles of the Opera" due to thinking she's losing her cuteness.
** Buttercup loses it in "Clawdad" while on a boat to catch a crawdad, in the time span of two hours.
* In the ''WesternAnimation/ReadyJetGo'' episode "Castaway Carrot", Carrot goes insane while stranded on the moon. He attempts to farm pizza on the moon, and gets lonely so he draws pictures of Jet, Celery, and Sunspot on some moon rocks. He even briefly makes out with the Celery rock!
* In ''WesternAnimation/{{Recess}}'', we have poor T.J. in "The Box". Miss Finster introduces a new form of discipline in the form of "the box", a white box on the pavement, where troublesome kids have to stand inside as punishment. When T.J. is sent to it, he quickly [[GoMadFromTheIsolation breaks]] and is eventually reduced to a blubbering mess who rocks back and forth singing "This Old Man", constantly does stuff for Miss Finster while chattering about how he's a "good boy", screams at the sight of anything square-shaped, and thinks the walls are closing in on him while in the box. Fortunately, he gets better.
* Rigby of ''WesternAnimation/RegularShow'' goes cuckoo when he learns the "Death Punch of Death", to the point where he's willing to drown in lava if it means beating Mordecai at "punchies".
* Ren of ''WesternAnimation/TheRenAndStimpyShow'' frequently falls into this. Stimpy sometimes does too. Their breakdowns range from hilarious to terrifying.
-->'''Ren:''' It's all so clear to me now! I've got it ''all'' figured out! I'm the keeper of the cheese! And you're the lemon merchant! And [[DrillSergeantNasty he]] ''knows'' it! That's why he's trying to ''kill'' us! We gotta get out of here, ''before he sets loose the marmosets on us''! Don't worry, little lady, ''I'll save ya''!
* ''WesternAnimation/{{Rugrats}}'':
** From [[WesternAnimation/TheRugratsMovie the movie]], Tommy totally snaps and almost pours mashed bananas on Dil, knowing the monkeys will be attracted to it. It's thundering and raining the whole time, and Tommy just starts acting more and more crazy as he starts ranting about how much Dil has ruined his life.
** In ''[[ItsAWonderfulPlot Chuckie's Wonderful Life]]", Chaz goes insane in a world without his son. Taking the death of his wife into account actually makes this scene even HarsherInHindsight.
** Stu also loses it in "[[Recap/RugratsS3E7WhenWishesComeTrueAngelicaBreaksALeg Angelica Breaks a Leg]]", when he's forced to take care of Angelica after she pretends to have broken her leg.
--->'''Didi:''' It's four o'clock in the morning, why on Earth are you making chocolate pudding?\\
'''Stu:''' ''[wearily resigned]'' Because I've lost control of my life.
* Fifty years of failure took a toll on WesternAnimation/SamuraiJack and his sanity as of Season 5; he gets frequent hallucinations of Aku's victims accusing him of having given up, and often argues with his subconscious as it tempts him towards less than moral actions (including once suggesting {{seppuku}} as a means of escaping his torment). Outside observers such as [[LargeHam Scaramouch]] or [[DarkActionGirl Ashi]] just see Jack arguing and pleading with empty space/rocks, concluding that the samurai has well and truly lost it.
* ''WesternAnimation/SheRaAndThePrincessesOfPower'':
** Light Hope hints that this is what caused Mara to deviate from her destiny. Subverted in season 3, when Adora learns that Mara wasn't insane and had legitimate reasons for hiding Etheria in Despondos.
** In season 3, Catra experiences this after her jealousy toward Adora pushes her to the breaking point. She activates the interdimensional portal, fully aware that it will destroy Etheria and herself, because she wants to deny Adora another victory. In season 4, multiple stressors (including guilt over exiling Entrapta, Scorpia's defection, and the emptiness she feels despite all the Horde's military victories) undermine her sanity. Double Trouble's BreakThemByTalking speech in "[[Recap/SheRaAndThePrincessesOfPowerS4E13DestinyPart2 Destiny, Part 2]]" leaves her broken and despondent.
** In "[[Recap/SheRaAndThePrincessesOfPowerS4E01TheCoronation The Coronation]]", Catra's lie about Entrapta's supposed "betrayal" triggers Hordak's nervous breakdown. He broods in the wreckage of the portal machine, demonstrates unsound judgment, and reacts violently to the mere mention of Entrapta. He regains his sanity for most of season 4, but when Double Trouble reveals to him that Catra exiled Entrapta, he attacks Catra in a [[RoaringRampageOfRevenge berserk rampage]].
* ''WesternAnimation/TheSimpsons'':
** In "[[Recap/TheSimpsonsS5E10Springfield $pringfield]]", Mr. Burns' sanity erodes the longer his casino stays in business, Ala Howard Hughes. He grows a shaggy beard, becomes a hypochondriac, and when things fall apart, expects him and Smithers to fly home in a tiny model plane.
** In "[[Recap/TheSimpsonsS6E1BartOfDarkness Bart of Darkness]]", Bart breaks his leg at the start of summer and begins to GoMadFromTheIsolation.
** Homer does so in the "[[Recap/TheSimpsonsS6E6TreehouseOfHorrorV Treehouse of Horror V]]" segment "The Shinning" when the cable stops working and they run out of beer, all thanks to Mr. Burns.
--->'''Homer:''' So what do you think, Marge? All I need is a title. I was thinking along the lines of "No TV and no beer make Homer something something"...\\
'''Marge:''' "Go crazy?"\\
'''Homer:''' '''''Don't mind if I do!''''' ''[proceeds to go crazy]''
** Frank Grimes learns the hard way in "[[Recap/TheSimpsonsS8E23HomersEnemy Homer's Enemy]]" that being the OnlySaneMan in a CrapsackWorld is not conducive to one's long-term mental health.
** Homer again in "[[Recap/TheSimpsonsS10E13HomerToTheMax Homer to the Max]]". When the whole town pesters Homer for sharing a name with a new, buffoonish TV character, he begins going crazy with paranoia and orders Bart to kill a cat and a flower for "laughing at him".
--->'''Marge:''' Homer, your growing insanity is starting to worry me.
** "[[Recap/TheSimpsonsS18E13SpringfieldUp Springfield Up]]" contains a very swift summary of how doctor/lawyer Eleanor Abernathy went off her rocker and became the town's yowling cat lady.
* ''WesternAnimation/TheSmurfs2021'': In the episode "Leaf It Alone", the Smurfs slowly go crazy from losing the Sarsaparilla. Some try to sacrifice Dimwitty to get it back.
* ''WesternAnimation/SouthPark'':
** "[[Recap/SouthParkS15E12OnePercent 1%]]" ends with the implication that Cartman's sociopathic tendencies are growing into full-blown psychosis. Even without any greater implications, you can see his sanity suffer with each stuffed animal destroyed.
** Randy in "[[Recap/SouthParkS16E12ANightmareOnFaceTime A Nightmare on Face Time]]", complete with a shot-for-shot, line-for-line {{homage}} to Creator/JackNicholson and ''Film/TheShining''.
** Randy's SanitySlippage is a recurring arc throughout the series, with him going from a BumblingDad to a selfish {{Manchild}}, and finally the deranged, murderous [[CorruptCorporateExecutive head of a weed farm]].
** Stan also undergoes this to a lesser extent in later seasons, becoming far more cynical and apathetic to the world around him after Wendy breaks up with him and the events of "[[Recap/SouthParkS15E7YoureGettingOld You're Getting Old]]". The ending of "[[Recap/SouthParkS15E8AssBurgers Ass Burgers]]" shows that he's resorted to using alcohol to get through the day.
* ''WesternAnimation/SpongeBobSquarePants'':
** In "[[Recap/SpongeBobSquarePantsS1E6MermaidManAndBarnacleBoyPickles Pickles]]", [=SpongeBob=]'s life takes a turn for the chaotic after a {{Jerkass}} customer claims that he forgot the titular condiment -- by which we mean he tries to cook his bicycle and hangs the toaster on his front door.
** In "[[Recap/SpongeBobSquarePantsS1E8SandysRocketSqueakyBoots Squeaky Boots]]", Mr. Krabs goes crazy when the squeaky noise of the rubber boots he gave [=SpongeBob=] becomes too much to bear.
** Poor Squidward. In between being the entire ocean's ButtMonkey and victim to the constant shenanigans of his next-door neighbors, [=SpongeBob=] and Patrick, it's no wonder he's been shown to break down into a sobbing wreck or fits of maniacal laughter when the AmusingInjuries and ever-present failures prove too much to handle. In "[[Recap/SpongeBobSquarePantsS2E1YourShoesUntiedSquidsDayOff Squid's Day Off]]", Squidward tricks [=SpongeBob=] into running the Krusty Krab all by himself while he takes a day off, but he keeps imagining [=SpongeBob=] destroying the Krusty Krab and repeatedly goes back and forth to and from his house. While taking a bath he hallucinates [=SpongeBob=] is watching him and runs off to the Krusty Krab wearing only bubbles.
** In "[[Recap/SpongeBobSquarePantsS3E4NastyPattyIdiotBox Nasty Patty]]", [=SpongeBob=] and Mr. Krabs try to keep their sanity when they believed they killed the health inspector. [[spoiler:It turns out that the inspector is still alive, and the Krusty Krab passes inspection.]]
** In "[[Recap/SpongeBobSquarePantsS3E13NewStudentStarfishClams Clams]]", after Mr. Krabs loses his millionth dollar, we see him slowly go completely insane. The cut back to Mr. Krabs, who begins giggling maniacally [[EyeScream and tears his two eyes out, using them as a jump rope]] is genuinely disturbing.
** [=SpongeBob=] frequently has Sanity Slippage to the point that you wonder whether he's exactly sane to begin with...
--->''[from "[[Recap/SpongeBobSquarePantsS7E2GrowthSpoutStuckInTheWringer Stuck in the Wringer]]"]''\\
'''Patrick:''' Hey, whatcha watchin'?\\
'''[=SpongeBob=]:''' ''[watching static on TV]'' My favorite show. ''[the TV dies]'' Ha, ha, I love that part!
** When [=SpongeBob=] decides to live with the jellyfish in "[[Recap/SpongeBobSquarePantsS1E9NaturePantsOppositeDay Nature Pants]]", Patrick, [[TheDitz who isn't all there in the first place]], goes ballistic, planning on catching [=SpongeBob=] and keeping him in a jar.
** Although she’s the OnlySaneWoman, Sandy has had a psychotic outburst in "[[Recap/SpongeBobSquarePantsS2E7PrehibernationWeekLifeOfCrime Prehibernation Week]]". Having been already stressed about getting everything ready before hibernation, she becomes highly distressed when [=SpongeBob=] points out that they only have 168 more hours of playtime. This prompts him to offer her his company until she falls asleep. Her first few activities are innocuous enough, but when they go biking through an industrial park, and find hay in a needle stack, [=SpongeBob=] runs away. Sandy jumps to the conclusion that he’s in terrible danger and forces everyone in town to help her look for him. When everyone is run ragged by the obsessive search with no rest, they run away too. Sandy then tries to find [=SpongeBob=] alone, demolishing the entire city while screaming for him.
* ''WesternAnimation/{{Stanley}}'': Elsie experiences one when she grows tired of waiting for the butterfly to emerge from its chrysalis in "Caterpillar Countdown." The longer the wait, the worse she gets, as she ''really'' wants to see that butterfly.
* ''WesternAnimation/StarWarsTheCloneWars'': In "[[Recap/StarWarsTheCloneWarsS5E11ASunnyDayInTheVoid A Sunny Day in the Void]]", Gascon becomes increasingly desperate the longer the group remains in the desert; he starts out as short-tempered and snappish, descends into melodramatic pleas for mercy after the group finds another wrecked ships, descends into a fit of broken laughter after he realizes they'd been going in circles, and eventually slumps into despondent philosophizing after deciding he's doomed. He recovers after finding a way out.
* ''WesternAnimation/StevenUniverse'':
** In "[[Recap/StevenUniverseS2E4SayUncle Say Uncle]]", Pearl, who is the logical (most of the time), brainy perfectionist of the team, becomes increasingly unhinged and suffers at least three mental breakdowns from dealing with WesternAnimation/UncleGrandpa's weirdness. This is even emphasized by a significant downgrade in her appearance and animation and major [[ChewingTheScenery scenery chewing]] by her voice actress. It overlaps with temporary Flanderization because while Pearl is susceptible to bouts of hysterics and irrational behavior, she's never lost it to this degree before or since.
** In "[[Recap/StevenUniverseS2E13ChilleTid Chille Tid]]", it is implied to have happened to Jasper after [[spoiler:she is trapped in Malachite by Lapis, when she sees Steven again, crawling towards Steven with an insane look on her face and a tone in which she sounds like she plans on eating him alive]].
** Peridot's stay on Earth has... not been good for her personal stability. Oddly enough, while in most cases of this trope there's a direct correlation between how conclusively one has cracked up and how much of a {{Jerkass}} one is, in the later stages of her SAN meter's decline, Peridot actually gets ''nicer'', to the point of [[HeelFaceTurn defying Yellow Diamond and officially becoming a Crystal Gem]]; this realization leads to her most impressive FreakOut.
--->'''Peridot:''' ''[into her tape recorder]'' I'm a traitorous clod! They'll never want to think about what I've done again!\\
''[sighs, rewinds recording]''\\
'''Peridot (recording):''' I'm a traitorous clod! I never want to think about what I've done again!\\
'''Peridot:''' ''[grins widely]'' YEAHAHAHAHA!\\
''[...]''\\
'''Steven:''' Peridot, are you gonna be okay?\\
'''Peridot (recording):''' I'm a traitorous clod! ''[rewind]'' --traitorous clod!\\
'''Peridot:''' ''[turns around with a maniacally cheerful grin]'' [[BluntNo NO!]]
* ''WesternAnimation/StevenUniverseFuture'' has a field day with this trope, enough to be mentioned separately from the original series.
** Beginning with "[[Recap/StevenUniverseFutureS1E1LittleHomeschool Little Homeschool]]", we are shown that Steven has an unhealthy amount of repressed anger, resulting in him [[spoiler:getting a new power where he turns pink and gains violent tendencies whenever he's angry]]. This trend continues throughout the series. Steven also seems to have an unhealthy obsession with helping people, which comes back to bite him later.
** In "[[Recap/StevenUniverseFutureS1E3RoseBuds Rose Buds]]" and "[[Recap/StevenUniverseFutureS1E4Volleyball Volleyball]]", Steven is shown to be experiencing repressed trauma related to [[spoiler:the whole Pink Diamond/Rose thing and all the horrible things she did]], which seems to be the other major trigger for [[spoiler:Pink Steven mode]]. As usual, Steven bottles up his feelings.
** In "[[Recap/StevenUniverseFutureS1E6AVerySpecialEpisode A Very Special Episode]]", Steven runs himself ragged trying to help multiple people at the same time, eventually collapsing from exhaustion. Unlike the other examples on this page, it's PlayedForLaughs, and [[spoiler:it's ambiguous how much of this episode is even canon anyway]].
** In "[[Recap/StevenUniverseFutureS1E7SnowDay Snow Day]]", it's revealed that Steven has a constantly busy schedule and refuses to ever take a day off.
--->'''Amethyst:''' Man, you had a better work-life balance when the Diamonds were trying to kill the planet.
** Steven's sanity [[WhamEpisode takes a nosedive]] in "[[Recap/StevenUniverseFutureS1E9LittleGraduation Little Graduation]]". He discovers that [[spoiler:Sadie has broken up with Lars and is now dating a person named Shep]], [[spoiler:the Suspects split up and Sadie is performing alongside Shep]], and that [[spoiler:Lars and the Off Colors are going into space after the graduation]]. Steven [[spoiler:has a mental breakdown]] over all of this, and accidentally [[spoiler:uses his powers to trap everyone in a dome]]. The cherry on the cake is that Steven [[spoiler:projects his issues onto Lars instead of admitting that he's the one who needs help]]. No wonder he [[spoiler:leaves Little Homeschool]], which makes it worse as he now feels that [[spoiler:he has no purpose anymore]].
** In "[[Recap/StevenUniverseFutureS1E10PricklyPair Prickly Pear]]", which is an even bigger WhamEpisode, Steven has taken up gardening, except [[spoiler:he named all his plants after people he knows and talks to them, even stating that the flower named Lars is stuck in the ground and can't run off into space]]. This is PlayedForLaughs, but the rest of the episode is '''not'''. Steven's pet cactus gets [[spoiler:used as an emotional punching bag for Steven to vent his bottled-up feelings on]]. This comes back to bite him when [[spoiler: the cactus learns to talk and starts repeating the things that Steven's said about the gems... right in front of them]]. This causes Steven to [[spoiler:get mad at and abuse]] the cactus, who does not take it well and attacks him, mutating into a botanical monstrosity. At the end of the episode, [[DramaticallyMissingThePoint Steven learns that]] [[spoiler:he shouldn't talk about his problems at all]]. The most heartbreaking part is that [[spoiler:the gems know something is wrong and keep reaching out to Steven, but he rejects their help because he feels like he can't talk to them.]]
--->'''Pearl:''' Is there anything you need to talk about?\\
'''Steven:''' [[spoiler:[[WhamLine I think I've said enough.]]]]
** In "[[Recap/StevenUniverseFutureS1E11InDreams In Dreams]]", Steven gets to spend some quality time with Peridot when they watch the reboot of Camp Pining Hearts, and when they find it lacking, Peridot comes up with the idea for Steven to dream a new and better reboot. Steven goes along with the idea at first, but quickly gets tired out and stressed [[spoiler:when his own issues start twisting the dreams in weird ways. Fortunately, this one ends a little better when the last dream has Steven literally spelling out that he's uncomfortable with the situation and Peridot, recording his dreams, realizes that she was pushing him too hard and he that he was willing to do anything just to have ''someone'' spend time with him so he didn't have to be alone]].
** Later, after getting to spend some quality time with Connie and reaffirming that he can still be her friend even with her new friends around in "[[Recap/StevenUniverseFutureS1E12BismuthCasual Bismuth Casual]]", Steven begins to worry that Connie moving away for college will leave him without her. Talking to both Ruby and Sapphire individually, [[spoiler:they convince him to propose which does not go well]]. This sets up "[[Recap/StevenUniverseFutureS1E14GrowingPains Growing Pains]]", in which Connie's mother gives Steven a check-up when his [[PowerGlows gem powers]] start going mad and causing him to swell randomly. She eventually discovers [[spoiler:that Steven's skeleton is cracked, and that all the events of the last five seasons might not have healed mentally and left Steven's body reacting to all stresses as if he was in danger of dying]].
** In "[[Recap/StevenUniverseFutureS1E14GrowingPains Growing Pains]]", Priyanka makes a diagnosis that Steven has been through so many high stress situations (both physically and psychologically) at such a young age, that his body chemistry reacts in a manner disproportionate to the stimulant. Simply put, the relatively minor Era 3 problems that he has been facing (his friends leaving to bigger and better things, Connie turning down his proposal, etc.) feel like the life-or-death scenarios of Era 2 to him, giving him anxiety attacks that manifest as PowerIncontinence.
** It eventually hits a point where he begins to put others in danger starting with "[[Recap/StevenUniverseFutureS1E15MrUniverse Mr. Universe]]", crashing Greg's van after giving him a TheReasonYouSuckSpeech for never giving him a proper childhood.
** In "[[Recap/StevenUniverseFutureS1E16Fragments Fragments]]", Steven seeks out Jasper and trains with her to control his powers in order to prevent them from causing any harm, but Jasper [[TheSocialDarwinist proves to be a bad influence on him]], with him getting progressively more and more ruthless to the point where his AllLovingHero traits completely disappear. His rematch with Jasper then ends with him [[spoiler:shattering her, though he's able to revive her later on]].
** In "[[Recap/StevenUniverseFutureS1E17HomeworldBound Homeworld Bound]]", it only gets worse. After realizing that White Diamond was the source for all his problems and trauma, Steven attempts to [[spoiler:'''shatter''' her by using White's puppet powers to force her head against a pillar. Afterwards, he begins to go under a transformation similar to the one he went through in "Fragments", but with his hair starting to resemble '''Pink's''']].
** Then, in "[[Recap/StevenUniverseFutureS1E18EverythingsFine Everything's Fine]]", [[spoiler:Steven goes completely off the rails. He returns after visiting the Diamonds, now stuck as the large, muscular man he became in "Fragments". He tries to head into Little Homeworld to help out and generally have a normal day, but his emotional state [[PowerIncontinence causes his powers to go completely haywire]], up until the point where an excited shout over a baseball he caught produces a shockwave that levels several buildings. Steven then heads back to the house, where Greg, Connie and the Gems are gathered for an intervention, which Steven... does not take well, his body starting to violently contort while he cries out in pain. When Connie proposes taking Steven back to the hospital, the Gems react in shock, because he never told them he went]]. Steven responds by playing down his issues all throughout ''Future'', likening his crashing the van to "a little disagreement" and a "rite of passage". In the same breath, he mentions that he almost murdered White Diamond and "only" shattered Jasper but thanks to his powers, he can fix everything with no one being the wiser. At this point, Steven collapses to the floor and proclaims himself a fraud, quietly sobbing to himself. Then he screams that he's a monster and the episode ends with [[WhamShot a mass of pink spikes bursting out of his back]].
* ''WesternAnimation/TeenTitansGo'': This happens to Robin in "Uncle Jokes" when [[ItMakesSenseInContext Starfire becoming funny affects the team's equilibrium]].
** Robin is prone to this in general. It's telling that [[HearingVoices the disembodied voice in his head]] is the ''sane'' one.
* ''WesternAnimation/ThomasAndFriends'': The Fat Controller, of all people, suffers this when he and Skiff are stranded "Skiff and the Mermaid". He becomes obsessed with survival on their small island - even though Skiff points out they're not far from port and can sail back once the tide changes.
* Starscream's near-death at Megatron's hands in ''WesternAnimation/TransformersCyberverse'' marks the beginning of a descent into over-the-top scenery-chewing lunacy. By midway through season 2 he's convinced that the scraplets he's created from the Allspark have the souls of Transformer legends including Alpha Trion and Zeta Prime in them, and that's not even the bottom of the rollercoaster.
* ''WesternAnimation/TransformersPrime'' showcases [[BigBad Megatron]]'s slow descent into (further) homicidal madness. Doping using the blood of [[{{Satan}} Unicron]] certainly hasn't helped, but he's clearly slipping even without it. It becomes most clear when he get the Dark Star Saber, whereupon he starts shouting about how he'll tear this world apart (despite the fact that doing that dooms the entire universe).
* In the WesternAnimation/DonaldDuck wartime short "WesternAnimation/TheVanishingPrivate", Donald is knocked into a barrel of [[InvisibilityInk invisible paint]] by Sergeant Pete and spends the rest of the cartoon trolling him. The General thinks Pete is losing his marbles when he sees him skipping around singing "Here We Go Round the Mulberry Bush" (in sarcastic imitation of Donald) and throwing flower petals (in the hope of revealing Donald's location); when Pete asks "Have you seen a little guy... that you can't see?" and then starts dancing around screaming (Donald having used a pair of pliers to drop a cactus down the back of his trousers), this just reinforces his belief. Donald's torment eventually ''does'' erode Pete's sanity, until he is running around the base with a double armload of live hand grenades. When the General tries to talk him down and Donald uses the General's sword to make Pete drop his grenades, the sergeant ends up in a straitjacket and padded cell.
* ''WesternAnimation/{{Wakfu}}'': Nox's StartOfDarkness OriginsEpisode confirms that he had one due to the Eliacube getting into his head, and it gets harrowingly depicted in the spirit of the trope image.
* Rabbit has experienced this at various times in the Disney ''Franchise/WinnieThePooh'' franchise, often having to do with Tigger. His thinking he has seven years bad luck because of a broken mirror in "Luck Amok" from ''WesternAnimation/TheNewAdventuresOfWinnieThePooh'' is just one of many, many examples. In fact, [[https://www.youtube.com/watch?v=NTLo1L6KDXc&ab_channel=BobLettuceTobbs here's a few of them]] from ''New Adventures'', the "Luck Amok" one included.
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