History SanitySlippage / FanWorks

* In the vein of the Cutie Mark Failure Insanity Syndrome described in the Western Animation section, ''Fanfic/The Audience'' by Reality Check states that Trixie herself is diving into one as her special talent isn't magic like most unicorns, but rather stage magic, illusions and theatrical personalities. The constant heckling, jeers and challenges towards her achievements that she was receiving were making her the JerkAss that she was portrayed as in canon.

[[AC:''Franchise/TotalDrama'']]
* Fanfic/TotalDramaStranded'': Briony gets a major one very quickly when [[{{Jerkass}} Calvin]] begins relentlessly bullying her.

[[AC:Unsorted]]
* ''Fanfic/ACrownOfStars'': Jinnai, this story's BigBad, became much more paranoid (and a big time megalomaniac) since he overthrew former BigBad Winthrop because he realizes that the same thing could happen again; only this time with ''his'' head on the chopping black.
* ''Webcomic/HetaliaAxisPowers'': Austria/Roderich Edelstein in the ''Fanfic/NineteenEightyThreeDoomsdayStories'' is portrayed for the most part as undergoing through this. His obsession in finding out [[HopeSpot whether Hungary survived]] [[WorldWarIII Doomsday]] grows increasingly desperate (and irrepressible) over time to the point that others eventually start wondering if he's gone delusional from grief. [[spoiler:He doesn't.]] It's also mentioned to have happened as well with Romano (hijacked by TheMafia as his brother's successor) and Poland (having his personality shattered).

* The final story of ''Fanfic/CalvinAndHobbesTheSeries'' has two separate plotlines: one concerning the return of [[KnightOfCerebus Thunderstorm]] and another concerning Franchise/{{the Slender Man|Mythos}} showing up. When the plots intersect, Thunderstorm starts displaying signs of this.

* ''Fanfic/ThousandShinji'': As the story progresses, the corrupting influence of the ''[[TabletopGame/{{Warhammer 40000}} Chaos Gods]]'' upon Shinji, Asuka and Rei increases, and they became more psychotic and unstable. Shinji and Asuka become increasingly violent, the latter descending into berserker madness during two months Shinji was missing, killing criminals every night to lessen her pain and loss, and Rei turns their apartment into a garbage-filled shrine to decay.
* Calvin goes a ''little'' crazy trying to watch a pug in ''Fanfic/CalvinAndHobbesTheSeries''.
* Jack in Part 1 of ''Cave Story vs. I.M. Meen '' and for good reason. After being trapped inside an insane pedophile's sick mockery of a yuri pairing fanfic between his girlfriend and his girlfriend's best friend, being forced to work a part-time shift at a restaurant called Diarrhea Bell, being forced to watch the two girls 2-Girls-1-Cup each other right in front of his eyes, and being tickle-tortured and thrown in jail, Jack lets loose with this underrated gem of a scene, cementing this story's status as one of the secretly best fanfictions of all time:
-->''"I am Jack. Woe is me for I am wrongfully imprisoned. I am Jack! Sad and unhappy am I without friends. BOO HOO!! BOO HOO HOO HOO!!! (blows snot into handkerchief and smears it all over the floor)"''\\
''"Emptiness wells up in my tortured soul. I'm going to...GOING TO...(vomits all over the floor)"''\\
''"I am Sue; I also am indeed BLEAUGH! (dumps mixture of random condiments and gross stuff on the floor)"''\\
''"I'm just Toroko but I'm gonna barf too, and the MUSTARD, MUSTARD BARF MUSTARD BARF!!! (dumps ketchup and mustard all over the floor)"''\\
''"(soaks hands with the combined mixture) BEHOLD the GOOEY SLOP of our SORROW! (smears it all over his face) IT IS...SLOBBER...DAMMERÜNG! THE TWILIGHT OF THE CONDIMENTS!!! (removes hands from face and screams to the heavens, palms facing skyward) WEEP FOR THEM, WEEP FOR THEIR SORROW-HO-HOHO-HOHH!!!"''\\
''[[CaptainObvious "Yes, Jack, my delicate psyche has come horribly unglued!"]]''

* In the vein of the [[WesternAnimation/MyLittlePonyFriendshipIsMagic Cutie Mark Failure Insanity Syndrome]] described above in the Western Animation section, ''{{Fanfic/The Audience}}'' by Reality Check states that Trixie herself is diving into one as her special talent isn't magic like most unicorns, but rather stage magic, illusions and theatrical personalities. The constant heckling, jeers and challenges towards her achievements that she was receiving were making her the JerkAss that she was portrayed as in canon.
* ''Fanfic/TotalDramaStranded'': Briony gets a major one very quickly when [[{{Jerkass}} Calvin]] begins relentlessly bullying her.
* From the sister story, ''Fanfic/TotalDramaSwitcheroo'', Missy gets an even bigger one.
* ''Fanfic/QueenOfAllOni'': Her [[ColdBloodedTorture encounter]] with [[EvilSorcerer Lung]] leaves [[VillainProtagonist Jade]] with some severe PTSD, which only worsens as time goes on. It finally culminates with her confrontation with Tohru in the Vault of Endless Night, which convinces her the heroes are all out to kill or [[SealedEvilInACan seal]] her, at which point she [[VillainousBreakdown snaps completely]].

* [[http://www.fimfiction.net/story/188516/the-abcs-of-fallout-equestria The ABC's of Fallout: Equestria]], a collection of short stories, has [[http://www.fimfiction.net/story/188516/10/the-abcs-of-fallout-equestria/irradiate-by-fallingsnow Irradiate]], witch tells the story of a mare who becomes a ghoul and slowly goes feral.

* The final story of ''Fanfic/CalvinAndHobbesTheSeries'' has two separate plotlines: one concerning the return of [[KnightOfCerebus Thunderstorm]] and another concerning Franchise/{{the Slender Man|Mythos}} showing up. When the stories intersect, Thunderstorm starts displaying signs of this.

* Nav starts showing signs of this in ''FanFic/DiariesOfAMadman'', as he becomes far more reckless and depraved over the course of the story.
* Spike goes through one throughout ''{{FanFic/Zenith}}'', which stems from his UndyingLoyalty to Twilight.
* ''Fanfic/LovedAndLost'': [[TheUsurper Prince Jewelius]] was [[MaskOfSanity hardly ever sane to begin with]], but after [[spoiler:Princess Luna thwarts his attempt to hang Celestia]], he gradually [[VillainBall undoes all the hard work of his manipulations]] by losing his composure, responding angrily to subsequent setbacks in his plans, putting forth less effort into restraining his BerserkButton [[GreenEyedMonster regarding the adoration directed towards Celestia and Cadance]], and reacting petulantly to dissension/disagreements from others.
* ''Fanfic/{{Memories}}'' has Serenity. When we first see her, she's like Pinkie Pie, a happy, cheerful, harmless, fun-loving, chaotic, {{Cloudcuckoolander}} of a prankster with a soft spot for Discord. [[spoiler: Then she dies and comes back to life.]] Cut to the epilogue and [[https://www.fanfiction.net/s/7656204/1/From-Here-to-Eternity sequel]] and she's [[spoiler: giving out {{Slasher Smile}}s, [[EvilLaugh maniacal laughter]], telling Discord that she wants to [[WeCanRuleTogether overthrow his mother and rule in her place]], and finally saying [[SlowlySlippingIntoEvil that together they'll kill Celestia]]]].
* In ''FanFic/BeingDeadAintEasy'', Seto Kaiba slowly loses his mind as the story progresses for a variety of reasons, including guilt over Joey's death, obsessively trying to find a way to save Joey, lack of adequate food and sleep, [=KaibaCorp=] not doing well, worry for his own life and Mokuba's, and [[spoiler:synchronization with the dying Joey]].

* In [[''http://www.fimfiction.net/story/243458/ave-sonata Ave Sonata'']], this is apparently why Sonata Dusk is TheDitz.

* ''Fanfic/TheRiseOfDarthVulcan'': The [[ArtifactOfDoom Alicorn Amulet]] ''should'' be doing this to [[VillainProtagonist Ted/Darth Vulcan]], and the fact that it doesn't appear to be is worrisome for the heroes. [[spoiler: Comments by WordOfGod, and in-universe by the Princesses regarding Ted's "True Self" being appalled at his actions, suggest that he was suffering from this even ''before'' he put on the Amulet, from years of convincingly pretending to be a cruel bully in order to avoid bullying himself. As such, the Amulet can't drive him insane, because he was never quite sane to begin with.]]

* In [[http://www.fimfiction.net/story/188516/the-abcs-of-fallout-equestria The ABC's of Fallout: Equestria]], a collection of short stories, has [[http://www.fimfiction.net/story/188516/10/the-abcs-of-fallout-equestria/irradiate-by-fallingsnow Irradiate]], witch tells the story of a mare who becomes a ghoul and slowly goes feral.

* This happens to some characters in ''Fanfic/TheInfiniteLoops'' due to the strain, frustration, and boredom of living through the same events many many times. Sakura is the poster child for this sort of thing, having gone off the deep end and lost all moral restraint due to having come to believe that nothing she does in the loops matters since the loop will just reset.
* Occurs in the ''[[WesternAnimation/TheLegendOfKorra Legend of Korra]]'' fanfic FanFic/BookFiveLegends. [[spoiler:Temuji’s]] plan in the final chapters seems half-thought out at best, and gets worse the longer they go without fulfilling it, culminating in a VillainousBreakdown worthy of Azula's.
* [[http://www.fimfiction.net/story/188516/the-abcs-of-fallout-equestria The ABC's of Fallout: Equestria]], a collection of short stories, has [[http://www.fimfiction.net/story/188516/10/the-abcs-of-fallout-equestria/irradiate-by-fallingsnow Irradiate]], witch tells the story of a mare who becomes a ghoul and slowly goes feral.
* In [[http://www.fimfiction.net/story/243458/ave-sonata Ave Sonata,]] this is apparently why Sonata Dusk is TheDitz.

* In ''FanFic/TheStoryToEndAllStories'', the villain has gradually descended into madness to the point that he is unrecognizable.
* Estee's ''FanFic/TriptychContinuum'' has one in ''[[http://www.fimfiction.net/story/173790 Permanent Record]]'', wherein a poor guard is driven to utter and absolute madness over time by the antics of the Cutie Mark Crusaders, eventually culminating in their utter certainty that everything which goes wrong is their fault. To be fair, though... usually it is.
* ''Fanfic/LePapillonRising'' takes Adrien Agreste from Miraculous Ladybug, and slowly twists him into a psychotic, obsessive, slightly sociopathic {{Yandere}} through use of the Butterfly Miraculous. It's worth noting that this is an AU where Adrien is the main villain.
* ''FanFic/TransformersAnimatedCybertronianGenesis'': One of the main focuses of the narrative for both the original story and its sequel is Megatron's slow descent into madness as his obsession with defeating Optimus Prime grows. Eventually, it becomes so bad that ''Starscream'' calls him out on it. [[spoiler:He only manages to snap out of it when Gigatron gets involved]].
* [[Franchise/MassEffect Miranda Lawson]] under goes this in ''[[https://www.fanfiction.net/s/11521278/1/It-Got-Loose-and-Killed-All-Our-Guys-The-Project-Lazarus-Story It Got Loose and Killed All Our Guys: The Project Lazarus Story]]'', brought on by a mixture of being asked to bring someone back from the dead, the Illusive Man randomly asking for her to add modifications to Shepard[[note]] In order: [[EnergyWeapon laser]] [[EyeBeam eyes]], [[{{Hermaphrodite}} a vagina]], making him a [[OurWerewolvesAreDifferent werewolf]], the ability to [[SuperSpit spit acid]], and [[BrickJoke a boob]](only one, though)[[/note]], dealing with [[OnlySaneMan her]] ([[HighTurnoverRate rapidly dying]]) [[SurroundedByIdiots co-workers]], and the sheer isolation.[[spoiler: She eventually declares [[DeadPersonConversation Dead Shepard]] her best, and only, friend, and feels betrayed when he comes back to life]].

* [[WasOnceAMan Reaper]] was already AxCrazy in [[VideoGame/{{Overwatch}} Overwatch]] canon. In ''[[FanFic/BreakMyHeartBreakYourHeart Break My Heart, Break Your Heart]]'', he gets worse. Way, way worse.
* ''FanFic/ThisBites'': During the Enies Lobby arc, Sengoku combines this with UnstoppableRage. Every piece of bad news that comes his way drives him closer and closer to the edge, and by the time he's finally on his way to the Judicial Island himself, he's basically in full-out VillainousBreakdown mode.
* Twilight and Pinkie Pie go though this in ''FanFic/BrideOfDiscord'', after Discord takes Fluttershy away, do to both losing a friend and in Twilight's case, working herself to the bone and refusing to rest, while trying to find any possible way of getting her back.
* ''FanFic/CodeGeassMegiddo'': Suzaku has been on a gradual descent to insanity after he murdered his father [[spoiler:to save Lelouch and Nunnally's lives]], but after Euphemia's death and the events that transpired as a result of that (including learning that his best friend was his ArchEnemy), that descent accelerated and never stopped. By the time the narrative truly starts, Suzaku's MaskOfSanity is barely holding on and begins to crack when Lelouch is kidnapped by the Black Knights, cementing his inevitably return as Zero, and full-on ''breaks'' when they finally confront each other at Pearl Harbor. At this point, several other characters have become aware of how insane Suzaku truly is, and believe that if Lelouch still cares for Suzaku, on ''any'' level, killing him would be ''merciful''.
* ''Webcomic/TeamRocketRoots'': After her favorite agent, Miya, went mysteriously missing while on a mission, Team Rocket's Madame Boss Gianna began slipping.

* ''Fanfic/RocketToInsanity'' is a fanfic where ''Fanfic/CupcakesSergeantSprinkles'' is a [[RecurringDreams recurring nightmare]] of Rainbow Dash's. It gets to the point where Rainbow Dash withdraws from her life and distances herself from everyone else. When Pinkie Pie tries to cheer up Rainbow with a cupcake, Rainbow snaps and kills Pinkie in what-she-thinks is self-defense.
* Satsuki undergoes this in chapter 5 of ''Come find me, again.'', due to depression over the loss of her sister. After noticing some changes, her parents make her come stay with them (or she'll be put in the hospital) and, when she's brought home, she gets worse, as she starts hallucinating, dancing on the widow's walk railing (almost falling off), and even broken glass (without shoes). Afterwards, she's hospitalized, where she starts to improve.
* In ''Fanfic/InfinityCrisis'':
** Daisy notes that the Red Skull must have gone insane after being trapped on that planet guarding the Soul Stone, but Steve simply observes that it would have been a very short trip.
** In ''Of Kryptonians and Queens'', Merlin states that whatever dark arts Morgana used to extend her lifespan over centuries made her more dangerous and twisted than before.
** In ''Gamma Relations'', Bruce immediately tells that Sterns' transformation into the Leader also drove him insane.
* Starting from about one-fourth into ''Fanfic/TheVerySecretDiary'', Ginny begins blacking out, sleepwalking, and behaving unusually enough that her family starts to worry. This is thanks to Tom Riddle [[ManchurianAgent possessing her without her knowledge]]. Ginny, not realizing Tom's responsible, confides in him, making it that much easier for him to {{Gaslight|ing}} her and make her question her own sanity. Once she finally realizes what's ''really'' going on, things get worse. [[ForegoneConclusion Much]], ''[[DoomedByCanon much]]'' [[VisionaryVillain worse]].

* ''Series/{{Supergirl 2015}}'' fanfic ''Fanfic/MyYouthIsYours'': Flashbacks show how Lex went from Lena's cool big brother who was very supportive of her relationship with Kara to a violent human-supremacist willing to do anything to take down Superman.
* ''Fanfic/FiresideTale'': Anna grieved over Elsa for the rest of her life. She was considered "mad". Even when Arendelle became uninhabitable and everyone else left, Anna stayed.
* ''Fanfic/KingdomOfIsolation'': Anna's brutal death takes a toll on Elsa. She shuts herself from everyone and creates a "perfect world" of snow people where Anna is alive and it's her coronation every day. Her parents and Anna are all alive while Hans is a pile of slush in the prison. In the real world, Arendelle is in turmoil because there's a raging blizzard.
* Platinum from ''Fanfic/ABriefHistoryOfEquestria'' suffered from this during the Winter War due to her plans for Unicornia falling apart. Clover had to lock her up in her chambers for her own good and take over the war effort. She broke out in time for the events leading to the Warming, and recovered after the Windigos were defeated.

* ''Fanfic/KaraOfRokyn'': According to Nasthalthia's story, her uncle ComicBook/LexLuthor used to be a hopeful, awkward, brilliant kid before running into ComicBook/{{Superboy}}. Lex initially befriended Superboy, but then he started blaming him for everything that went wrong in his life. At the beginning Lex merely wanted to show Superboy off, but as his obsession grew Lex gradually became madder, more irrational and more twisted, and quite soon he was plotting ways to murder his ex-buddy. When the proper story begins, Luthor has lost any redeeming qualities and is nothing but a ruthless, cold psychopath overwhelmed by inexhaustible hatred.
* In ''WebVideo/DragonBallZAbridged'', Piccolo and Vegeta suffer this when they spend time in the Hyperbolic Time Chamber by themselves. Piccolo starts hallucinating Cell after spending some time in there and decides that's enough training. Vegeta's the strange one as he resorts to a broomstick and a volleyball made up to look like Nappa after three days. In real time. Mr. Popo changed the time dilation in there, most likely in revenge.

* ''Fanfic/TheRavensPlan'':
** Stannis' time in the Black Cells has clearly damaged his psyche. By the time Robert and Renly visit him, he's seething in rage at the very sight of them, demanding to understand why it is that he's always been TheUnfavorite out of the three of them and wondering what Renly could have possibly done to earn Brienne's UndyingLoyalty, and when he learns about Jon Snow's true identity, he starts laughing at them before proclaiming himself to the "one true king of Westeros, Jon Targaryen".
** Lysa was hardly the picture of good mental health before the [[PeggySue Remembering]], but ''after?'' She's madder than the Mad King and a threat to herself as much as she is to everyone else. It's so bad that Yohn Royce currently has her drugged to the gills with milk of poppy for everyone's sake.
** Much like Lysa, Cersei wasn't all there to begin with, but after she's thrown into the Black Cells she starts losing her mind. Not helping the matter is Robert, who is deliberately tormenting her as payback for their toxic marriage.
* ''Fanfic/FireDarkMark'': Firebrand was never the most stable villain, but he endeavoured to be a cold, cunning schemer. When his father dies, though, Firebrand completely loses any semblance of sanity and develops a "Kill them all" mindset.

* In ''Fanfic/AmongUsInCharacter'', Drama slowly loses it after she continuously fails to catch the killer, and dreams of her dead crewmates each night. [[spoiler:It's later revealed this was the result of an alien parasite that infected her, which was slowly breaking her mind to take control of her. [[FaceMonsterTurn It succeeds.]]]]

* Jack O'Lantern, the ArchEnemy of ''FanFic/UltimateSpiderWoman'', commits increasingly violent and destructive crimes as the series progresses. He goes from robbing banks to taking people hostage to going on killing sprees to orchestrating a bloody city-wide MobWar. Even in jail, we see him fantasizing about carving up human heads the way people do Halloween pumpkins. What's unusual is that Jack always had these sadistic urges-the Sanity Slippage comes from the escalating nature of his crimes.

* In ''Fanfic/AmazingFantasy'', Years of constant defeats turned the already self-centered Mysterio into an individual obsessed with being seen as something more than the guy who Spider-Man beats, resulting in him committing much darker crimes on in both Izuku's and Peter's universes.

* ''Fanfic/VivaLaVida'': Olive gradually starts to slip in both alliance and mental health over the course of the story, with her conflicting emotions causing her to lash out at those around her. And with her only attempt at reaching out to someone for help going horribly wrong, she eventually completes her FaceHeelTurn and goes to the odd side in full (in the BadEnding, at least). Chapter 4 even implies that Olive is completely unaware of her thoughts or actions when it comes to viewing Odd Todd as an ally rather than as an enemy.
* ''Fanfic/AFrozenFlower'': When you're an awoken ''lambero,'' there is absolutely no such thing as being sane all the time. Orchid is living proof of that — when her powers are triggered and begin going out of control, she experiences pain and begins to inadvertently destroy the room she's in and kill the life that's around her, while also [[{{Hallucinations}} hallucinating vividly.]] And that's to say nothing of the process of [[SuperPowerMeltdown "shelling out"]], which is essentially a ''lambero'' having their sanity dip the more they use their powers. A severe shellout can cause a ''lambero'' to either go completely insane, or in the worst case scenario, be killed by it, the latter of which became the case with Oz.

* ''[[https://archiveofourown.org/works/37736467/chapters/94213441 Lila Rossi: Queen of Lycée]]'': Lila's obsession with being popular works against her when she becomes obsess with beating Juleka for Prom Queen, and gets seen as crazy for wanting to win against a girl who lost her leg in a car. Her fall from grace when she gets exposed as a liar and blackmailer only makes her far worse. In the last two chapters, [[spoiler:this ultimately leads her to murdering everyone that had a part in exposing her, with [[FinalGirl Juleka]] barely surviving by naming Lila as Prom Queen, with the AxCrazy girl celebrating her victory even as she is arrested by the police. The story ultimately ends with Lila in a mental institution, proclaiming that she is [[TitleDrop the queen of lycée]] [[MadnessMantra over and over again]]]].

* ''Fanfic/TheRingingInMyEarsGetsViolent'' employs this throughout Leon's ApocalypticLog, depicting his deteriorating mental state and growing LossOfIdentity in true '' Franchise/ResidentEvil'' style. By the time Chris finds his last note, it's barely sensible enough to be read. A later section from Leon's POV depicts how [[BrainwashedAndCrazy broken and erratic]] his mental state is, by the time of the story.
* ''Fanfic/TheDeathEatersDisneyWorldTrip'': The entire titular trip is described to be one to the Death Eaters, and to Snape in particular due to his status as the OnlySaneMan. [[LampshadeHanging Chapter 7 is even titled "Dwindling Sanity" by the author.]]

[[AC:''VideoGame/SpecOpsTheLine]]

* ''Fanfic/DearJournalImCrazy'': As a result of him running out of medication, the things he saw, from his peers' abnormal skin tones to Skeeter's honking, slowly come back to haunt him. It all comes to a massive Freak Out weeks later, leading to Doug being committed to a psych ward.
* ''[[https://archiveofourown.org/works/37736467/chapters/94213441 Lila Rossi: Queen of Lycée]]'': Lila's obsession with being popular works against her when she becomes obsess with beating Juleka for Prom Queen, and gets seen as crazy for wanting to win against a girl who lost her leg in a car. Her fall from grace when she gets exposed as a liar and blackmailer only makes her far worse. In the last two chapters, [[spoiler:this ultimately leads her to murdering everyone that had a part in exposing her, with [[FinalGirl Juleka]] barely surviving by naming Lila as Prom Queen, with the AxCrazy girl celebrating her victory even as she is arrested by the police. The story ultimately ends with Lila in a mental institution, proclaiming that she is [[TitleDrop the queen of lycée]] [[MadnessMantra over and over again]]]].

* ''[[https://archiveofourown.org/works/37736467/chapters/94213441 Lila Rossi: Queen of Lycée]]'': Lila's obsession with being popular works against her when she becomes obsess with beating Juleka for Prom Queen, and gets seen as crazy for wanting to win against a girl who lost her leg in a car. Her fall from grace when she gets exposed as a liar and blackmailer only makes her far worse. In the last two chapters, [[spoiler:this ultimately leads her to murdering everyone that had a part in exposing her, with [[FinalGirl Juleka]] barely surviving by naming Lila as Prom Queen, with the AxCrazy girl celebrating her victory even as she is arrested by the police. The story ultimately ends with Lila in a mental institution, proclaiming that [[TitleDrop the queen of lycée]] [[MadnessMantraover and over again]]]].

* [[WasOnceAMan Reaper]] was already AxCrazy in [[VideoGame/{{Overwatch}} Overwatch]] canon. In ''[[FanFic/BreakMyHeartBreakYourHeart Break My Heart, Break Your Heart]]'', he gets worse. [[UpToEleven Way, way worse.]]

* ''Fanfic/RocketToInsanity'' is a fanfic where ''Fanfic/{{Cupcakes}}'' is a nightmare of Rainbow Dash's. She keeps on having it over and over again. It gets to the point where Rainbow Dash withdraws from her life and distances herself from everyone else. When Pinkie Pie tries to cheer up Rainbow with a cupcake, Rainbow snaps and kills Pinkie in what-she-thinks is self-defense.