There are many causes for insanity. Too many, honestly. However, insanity does have its limits; specifically, if you go past 32,767 you roll over the "insane-o-meter" and go back to being sane. Other characters simply grow bored with being insane and choose to become sane again. So they do.
Usually, this is more of a throwaway piece of dialogue or plot to explain how a character has managed to go back to normal or left the ranks of Cloudcuckoolanders. Of course, it is by definition uttered by an Unreliable Narrator, so they may or may not be as sane as they claim.
- Seemingly happened to Johan in Monster. He has been a mass murdering psychopath for pretty much all of his life, but he seems to have become pretty nonchalant about all the evil plots and groups that revolve around him and the possibility that he is the Antichrist. He has seen a vision of The End of the World as We Know It several times, and while other characters are either horrified or entranced by this, he has grown weary of it and doesn't regard it as a big deal any more. His suicidal impulses can be traced to boredom with his own sociopathy.
- Many of the Awakened Beings that have been around longer in Claymore seem to be like this, as comparatively younger ones like Ophelia or Priscilla are completely insane, while older ones like Rigardo or Riful just seem bored with existence.
- Fate/strange fake: Flat Escardos summons Jack the Ripper as False Berserker. While normally, a Berserker is a lunatic, Jack is perfectly calm and rational, and remarks that he has clarity that he would not normally have. Flat compares it to how a negative number times a negative number equals a positive number; the Berserker Class' Mad Enhancement Skill may have canceled out Jack's insanity.
- JLA: Plastic Man on the 3000 years he spent scattered across the ocean floor: "Being crazy got boring after the first 1000 years, so I started writing poetry."
- The Joker's done this multiple times, to the point that the character is often portrayed as "super sane", not being nearly as crazy as everyone else is. Whenever Batman appears to die, in fact. Or once when faced with an Eldritch Abomination.
[after witnessing an explosion that kills his nephew] ...get my toga.
- Grant Morrison has had characters speculate that the Joker has a kind of super-MPD, so he reinvents his own personality every few years. One year he'll just go with practical jokes, the next year he won't kill anybody, the next he'll kill everybody... (Granted, said characters who forward these theories aren't exactly sane themselves.)
- Maxie Zeus, in Batman: Cacophony, dropped his "I am Zeus" delusion and cut all ties with the Mafia (or so he claims - he's still in touch, just not ranting at them in full regalia). A visit from the Joker has him snapping back.
- Mr. Myxzptlk is said to go through cycles like this every few eons in Whatever Happened to the Man of Tomorrow?, where he claims to feel he's been random, chaotic, and "silly" for too long, and is just going to be evil for a few millennia.
- Deadpool did this apparently, in an alternative future featuring in a run of the X-Force series while Cable was raising Hope. He hides in a meat locker, gets buried within it, goes insane, plays tic tac toe for a few hundred years, gets bored, plays hangman against a split personality he developed on purpose in order to be able to play hangman (complete with a college graduation hat), decides his other personality is too intelligent and kills it, and then gets bored, goes sane, more or less, and gets freed by a bunch of scavengers. All in 800 years. "Sane" is a relative term for Deadpool.
- In Sonic the Hedgehog, Dr. Eggman pulled off something similar in the ten issues following his descent into insanity in #200. A stray rebuke by another character caused the delusional doctor to begin to mumble and ponder, and seemingly through free-association, brought himself back to sanity, or at least a functional level of madness.
- Played with as part of one Bleach fanfiction. The main character became a Hollow while maintaining his human mind; the stress of realizing he was a monster that needed to devour souls to survive drove him to insanity. Eventually the insanity broke and he tried other methods of passing the time that involved less murders.
- Child of the Storm has Harry remark a couple of times that he tried insanity (specifically, becoming the Dark Phoenix after a brutal Trauma Conga Line, though being possessed by Chthon had a similar effect) and that he got bored with it. This gives him the ability to calmly and clinically analyse all kinds of horrific and Mind Screw type situations without being remotely fazed, with his grandmother, Frigga, observing that his ability to discuss such extraordinary things in such a casual way is one of the most extraordinary things about him. However, it's also made plain that he has limits in this regard.
- Doing It Right This Time: Asuka had gone through huge emotional and psychological trauma during the original timeline (her mother's madness and death; her father's adultery and abandonment; people using her like a doll; her surrogate family and friends hurting her, betraying her or leaving her; constant beatings, humiliations and even a Mind Rape at the "hands" of alien monsters; the boy she liked treating her as masturbation fodder after spending months clueless to her hints; getting chopped into pieces and eaten alive...) and it had rendered her mad and unstable. Even though she survived the end of the world, she was so broken she decided to kill herself. Then she got sent to the past. She was so thrilled with having a second chance she decided to forget about her mental issues and start from scratch. In an outdated version of a scene of the second chapter she blatantly says she got bored of being crazy.
Asuka: Oh mein gott you remember!
Hikari: I was so scared you wouldn't, [...] Or worse, you would and you'd be so broken I couldn't reach you...
Asuka: Who, me? Yeah, right, like I could stay crazy forever without getting bored of it. Oh, it's so good to see you again!
- The Infinite Loops: In the Warhammer 40,000 Loops, the looping Chaos Gods aren't a threat because they're bored with Chaos's original emotion-warped insanity and they don't want to do everything again.
- In The Crazy Family, after the insanity comes to a head with an explosion, the family settles down to have breakfast.
- In Evil Dead 2, the evil spirit which torments Ash shatters his sanity more than once, forcing him to kill his girlfriend, sever his own hand, and leaving him shouting in Angrish and laughing hysterically in the cabin while a mounted deer head, rocking chair, and even a desk lamp all laugh with him. Once visitors from the outside arrive and start dying, he gets somewhat better.
- In Groundhog Day, the endless repetition of February 2nd causes Phil to go through a breakdown period where he repeatedly tries to kill himself and, when that doesn't work, declares his Godhood to Rita. He eventually settles down and becomes rather zen about the whole thing. So at ease with the whole thing does he get that he finally gets his one perfect day with Rita and snaps out of the loop, a much better and saner person for it.
- Invoked, in a sense, by Harry Dresden in The Dresden Files. Harry views the pure essence of one of the evil creatures on Earth, and the immutable image of it knocks him unconscious and nearly drives him insane. Harry's response is to get to a quiet, dark room and repeatedly hammer his brain with the image of the monster until it loses all impact on him. Years later, Harry still stumbles in his speech when he occasionally remembers the monster, but it can no longer drive him to the edge like it used to.
- Animorphs: The kids remark from time to time that the only thing they find strange anymore is that they don't find anything strange anymore. Constantly lampshaded by Marco, who often remarks, deadpan, on how utterly insane their lives have become. Let's see: started with aliens, added shapechanging, destroyed some spaceships, traveled through time...again, manipulated by god-alien, bartered hair and holograms for tour guide on distant planet, the oatmeal issue...and that's just the beginning.
- The Hitchhiker's Guide to the Galaxy
Arthur: This is you sane again, is it? I ask merely for information.
- Arthur Dent in Life, the Universe and Everything decided to go mad after being stranded on prehistoric Earth for a few years and Ford Prefect tells him this is a good idea (but that insanity is a gradual process and he shouldn't rush). Ford also says that he went mad for a bit and spent several months thinking he was a lemon and jumping in and out of a lake that thought it was a gin & tonic (at least he thinks it thought it was a gin & tonic... he may have been imagining it). Then he got bored with that, went sane, and tried to learn to fly.
- Wonko the Sane in So Long, and Thanks for All the Fish. Considering he believes that everyone is insane, and he decided to go sane and build a nice little asylum for everything in the universe save for himself, a small house, and the Pacific Ocean. Whether he is this or not depends on whether you agree.
- The controversial and sometimes-cut 21st chapter of A Clockwork Orange has Alex outgrowing his sadism because he's just not that interested in "the old ultra-violence" anymore.
- Distantly related: Gabriel Syme from G. K. Chesterton's The Man Who Was Thursday. The family he's born into is so full of social radicals, political radicals, religious radicals, and miscellaneous crackpots that when he reaches his teenage years, the only way he can rebel against his family is to become normal.
- Terry Pratchett is fond of this: the obvious example is Vorbis from Small Gods.
- Also with Jeremy Clockson in Thief of Time. Without medication, he becomes too sane.
Obviously, he reasoned, if sticking screws up your nose was madness, then numbering them and keeping them in careful compartments was sanity, which was the opposite-Ah. No. It wasn't, was it...
- His Igor doesn't think he's sane (there's a short section where he wonders if he finally got a sane master, but... ah, no). It is, however, likely that without his meds, Jeremy goes straight through sanity into... ytinasni?
- Similarly, the Bursar of Unseen University is so insane that he sometimes hallucinates that he's sane. In fact, the other wizards keep him well supplied with hallucinogens to keep him thinking he's sane, so he is. Apparently, this is a very common hallucination, one shared by most people.
- Pratchett also has the very fun concept of knurd, which is like being drunk except in the other direction. Being very knurd makes you see things exactly as they are, which is enough reason for most people to start screaming and never want to be knurd ever again. Vimes was born slightly knurd, needing a stiff double just to be sober, which as he no longer drinks explains his cynical outlook before and after. This is an actual medical condition in real life, too. (The being naturally drunk, that is.)
- The duke in Wyrd Sisters alternates between this and being a complete and utter loony. The relevant quote is:
"The duke's mind ticked like a clock, and, like a clock, it regularly went cuckoo."
- In The Art of the Discworld, Pratchett says that when your grandfather is Death you either have to go totally mad or completely sane. Susan's case is the latter.
- Also with Jeremy Clockson in Thief of Time. Without medication, he becomes too sane.
- Nakor from The Riftwar Cycle books often seems to be only marginally sane, except when something important is happening, in which case he becomes absolutely lucid. It's later revealed that he has in his possession an artifact that can reveal any and all knowledge at the cost of the owner's sanity, but "you can only be crazy for so long" and he's had it for a very long time...
- Very bad things have been happening to Colonel Jax on a sentient hospital ship in Alastair Reynolds' short story "Nightingale". He's been surgically altered into a human artwork intended to represent the horror of war. When told that he seems proud of the results (though still quietly crazy), he responds, "Would you rather I screamed? I can scream if you like. It just gets old after a while."
- Ishamael, The Dragon for the Dark One in The Wheel of Time. When we first see him he is easily angered, has No Indoor Voice, and is basically inhuman, and he's so gone so insane that he believes he is the Dark One. After he dies and gets a new body, he's reached the other side of insanity; his new incarnation Moridin is a calm, patient Chessmaster who regularly draws on the True Power, which is supposed to be addictive and madness-inducing, with no negative side-effects. He's still a nihilistic Omnicidal Maniac, but he's perfectly logical and philosophical in his reasoning. He gradually degrades back toward his original personality- the cost of being Drunk on the Dark Side.
- In the last chapter of Don Quixote, a poster boy for Loony Fan of Chivalric Romance, his Fan Disillusionment is so great that he gets Bored with Insanity and comes back to his senses.
"I was mad, now I am in my senses; I was Don Quixote of La Mancha, I am now, as I said, Alonso Quixano the Good"
- Buffy the Vampire Slayer:
- Drusilla is briefly cured of her lunacy in two separate occasions and even tries to do some good for people during the latter incident. However, due to Status Quo Is God, it doesn't last.
- At the end of Season 2, Buffy is forced to send Angel to Hell to save the world. When he returns in Season 3's "Beauty and the Beasts," he's been driven insane by torture and spends most of the episode in a crazed, animalistic state but when he breaks free of his chains and kills Pete, he calms down, turns to Buffy... and says her name before breaking down in tears and hugging her.
- In early Season 7, Spike has been driven crazy by by his soul and newly restored conscience, as well as harassment from the First Evil. With Buffy's help, he's able to shake it off. Angel lampshades and complains about it in "Just Rewards":
Angel: You asked for a soul, I didn't! It almost killed me! I spent a hundred years trying to come to terms with infinite remorse! You spent three weeks moaning in a basement, and then you were fine! What's fair about that?!
- On Heroes, Sylar's biological father was, much like his son, a Serial Killer driven by a Horror Hunger to hunt down other superpowered people and steal their powers. According to him, one day he just realized how meaningless all the killing and power accumulating was, found an Addiction Displacement in taxidermy, and just quit. Then he sees Sylar demonstrate a Healing Factor that could cure the lung cancer he is slowly dying of, and he has a reaction much like an alcoholic being taunted with a free bottle of Johnnie Walker Blue.
- Sylar does this at least once a season, after previously having jumped off the deep-end.
- In Oz, Peter Schibetta goes insane and back twice.
- He doesn't seem to be fully back the second time, tho.
- Tobias Beecher goes through an insane phase. Unlike Schibetta, he's never sent to the psych ward.
- In season 5 of The A-Team, Murdoch is declared sane. The matter of whether or not he was ever insane was treated with ambiguity and inconsistency.
- The 1999 TV miniseries Noah's Ark has a variant: Noah, his three sons, and their wives all gradually Go Mad from the Isolation on the boat. But when Noah's wife finally cracks, or appears to, the other seven are so horrified that they abruptly go sane again.
- In The Flash (2014), this is one of the reasons Zoom created the persona of Jay Garrick and pretended to be the heroic Flash of Earth 2. The other reason was For the Evulz.
- Mickie James debuted on Monday Night Raw, as a Loony Fan obsessed with Trish Stratus. Eventually the obsession turned into a jealous guarding, with Mickie attacking anything or anyone she thought might be taking more of Trish's attention than her. Then when Trish got uncomfortable with Mickie putting her head too close to her crotch for too long a time, James snapped, at first vowing to break Stratus for breaking her heart before settling on trying to replace Stratus by dressing up as her, dying her hair and stealing her boyfriend. When Stratus decided to then dress as Mickie and play the part of the annoying fan, James quickly realized she had been acting a little crazy and that she didn't need to focus so hard on Trish.
- Sami Callihan had long come to realize he was little "weird" by the time EVOLVE started up but had also come to embrace it, loudly updating anyone who would listen about his ever changing obsessions. Then he got suspended for attacking El Generico and was deeply remorseful, vowing to go on a redemption quest to make up for it during his banned days. It wasn't until Dave Finlay beat some sense in Sami that he realized obsession and insanity were problems though. And despite gaining a desire to be sane, he still really wasn't.
- Dark Eldar from Warhammer 40,000 are all nightmarish hedonists. Every now and then, a Dark Eldar grows weary of the cruelty, the backstabbing (literal and figurative), and the empty hedonistic thrills that make up the average day in Commoragh. Occasionally these Dark Eldar end up embracing life on one of the Craftworlds whose lifestyle is nearly the complete opposite of what Dark Eldar life is like.
- Arcueid of Tsukihime (Near Side routes) goes through this (in the course of one night, nonetheless!) after being "killed" by an out-of-control Shiki. Except she's a True Ancestor vampire, and arguably the most powerful being on the planet. So instead of dying she lies there regenerating, then goes to look for vengeance - until she starts to wonder about who he is, and what kind of person he's like...
Arcueid: "It was so painful, I thought I was going to go crazy. However, the pain was so great, it restored my sanity. Do you know what it's like experiencing that over and over for a whole night? So, full of hatred, I went out to look for you. (...)"
Shiki: "...... I don't get it. If you hated me so much, why are you forgiving me?"
Arcueid: "—-Let's see... to put it simply, I calmed down after a while."
- Fujiwara no Mokou from Touhou. We only meet her after she's calmed down, but apparently she spent 300 years in a state where she could only preserve her sense of identity by killing everyone she met. And then got bored of that so she spent 300 years doing nothing. And then she got better.
- Tomb Raider (2013): Lara theorizes at one point that Mathias is "so beyond crazy that maybe he's come right back around to some kind of sane."
- Subverted in The Elder Scrolls IV: Oblivion as rather than being caused by boredom, Sheogorath was cursed by the other Daedric Princes to undergo this during the Greymarch every thousand years. The curse causes him to briefly revert to his original self as the Daedric Prince of Order, Jyggalag and destroy the Shivering Isles, only to lose his mind again afterwards and become the Mad God once more. During the Shivering Isles DLC, Sheogorath requests the Champion of Cyrodiil's aid in helping him prevent the latest Greymarch.
- Played with in The Elder Scrolls V: Skyrim, where Sheogorath remains a Cloud Cuckoolander, but is noticeably calmer and more inclined to Pet the Dog than before. This is heavily implied to be because they are really the Champion of Cyrodiil, who became the new Sheogorath at the end of Shivering Isles and chooses to be a far more benevolent deity than their predecessor.
- Faust of Guilty Gear. Once a brilliant doctor until a young girl died on his operating table, then the guilt drove him insane and he became a psychotic serial killer named Dr. Baldhead. One day, he had a vision from the girl saying that her death wasn't his fault and that she was assassinated, so he had a major Freak Out from the revelation and disappeared. Now he's back, he's sane, he goes by Faust, he wears a paper bag over his head, and he's no longer Ax-Crazy. Downplayed in that he's not completely sane and the old bloodlust is still there, just held back by his self-control.
- At the Chat-based RPG On Rails, ran on the messageboard Casa Dos Jogos, the Reality Warper (but that for some reason couldn't use his powers, them being controlled by his Enemy Without - that is trying to do an evil Split-Personality Takeover, by the way) Loki went crazy through the story, specially after getting his powers and failing to use them when their lives where at risk (reason already mentioned). After years in-game (centuries, actually) he finally snapped - again, and regained his sanity, going from a Cloudcuckoolander Plucky Comic Relief always trying (and failing) to use his powers either in battle or on Mundane Utility to a Only Sane Man Jerkass hated by even his player. Of course, it has been hinted, with him acting as a Jerkass anytime his Enemy Without is around even before coming back from crazy, and acting full-jerkass on an Lotus-Eater Machine scenario - not counting the fact the fact that said Enemy Without is a much more charismatic jerkass (not counting God-Mode Sue and Manipulative Bastard), to Ensemble Dark Horse proportions.
- Professor Paradox from Ben 10. His debut episode in Alien Force called (wait for it) "Paradox" has him explain that he lived trapped in a no-man's-land outside of time at the edge of a black hole for almost one hundred-thousand years, completely aware and not aging, after a time travel experiment went wrong. He went insane at first, then became tired of that, and became sane again. Very sane, as he put it, to the point of seeing reality exactly as it is, allowing him to become a Time Master.
- Vandal Savage in Justice League, becomes self-conscious of his own mental instability in the Bad Future depicted in "Hereafter", where his megalomania caused the ruination of the solar system and the extinction of the human race, causing him to spend the next 30,000 years utterly alone. As he bitterly admits, destroying the world and realizing he'd gone too far was just the catalyst needed to force him to become a better man.
Superman: Self-help books? You don't seem the type.
- Puck from Gargoyles noted that for all his centuries being The Trickster, he had never tried the role of the Straight Man—which is why he invented the identity of Owen Brunett.
- This is essentially the goal of exposure therapy: by exposing someone to their triggers in a controlled manner and environment, the patient eventually grows desensitized to them and, ideally, bored by them to the degree that their fear either goes away or becomes manageable.