Mask of Sanity

Robert: Take it from me: A very good sign that you're crazy is an inability to ask the question, "Am I crazy?"
Catherine: Even if the answer is "yes"?
Robert: Crazy people don't ask, you see?

— Proof

Some people laugh as a sign of mental instability. Others speak in a Creepy Monotone or openly show signs of being violent.

Then there's the character who's revealed to be insane and shows almost no signs of being crazy until that point... at least not publicly.

A character that feigns sanity quite simply is the kind of person that can maintain their façade in most social situations but is completely insane on the inside. So naturally when the audience figures this out it can sometimes be a major Plot Twist. Other times the character's craziness could be apparent to the audience from the start, and not the other characters. Either way beware of spoilers.

The Trope Namer comes from a book called The Mask of Sanity, which describes how people that aren't stable can blend in with society.

Yandere, Uncanny Valley Girl and Cute and Psycho are Sub Tropes, when people may act perfectly normal until that certain trigger is pressed, then they quickly turn into murderous psychopaths. Taking off the mask can be seen as a Villainous Breakdown.

Compare and contrast with Stepford Smiler (Unstable). Often overlaps with Reluctant Psycho. Contrast with Obfuscating Insanity. See also Beneath the Mask and Hyde Plays Jekyll.

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Examples

Anime & Manga

• Fullmetal Alchemist:
  • Solf J. Kimblee maintains his polite and empathic façade despite being a sociopath who is heavily implied to have pretended to be sane in order to join the military.
  • Shou Tucker, the Sewing-Life Alchemist, doesn't seem to fit the definition of a Mad Scientist as he's a calm and polite man. Then the Elric brothers find him in his laboratory with a chimera that understands human speech, but it sounds depressed and speaks dysfluently. Edward Elric soon figures out that he had used bioalchemy on his own daughter Nina and her Big Friendly Dog to create it, resulting in a miserable abomination in constant pain, and had done the same thing to his wife two years ago, driving her to suicide by starvation. At this moment, Shou drops his façade and reveals his true personality: an insane man with no emotional empathy, who prioritizes fame and fortune by researching and performing bioalchemy over the well-being of his own family and is unable to understand why anybody should care that he used them as scientific experiments.
• Seemingly played straight with Itachi from Naruto, who appears as stoic individual and is seemingly composed. That is until Sasuke sees his inner self in their final battle, in which he reveals himself as an Ax-Crazy power hungry sociopath ranting to surpass Madara Uchiha. Subverted later on after it's revealed that Itachi was intending to die by his brother's hand all along, and was playing the part of an unrepentant psychopath in order to provide Sasuke with further motivation to kill him.
• Gankutsuou: Andrea Cavalcanti at first seems like an effortlessly charming gent but is eventually revealed to be outright deranged to the point of seducing his mother and almost raping (or does he really?) his half-sister and stabbing his father.
• Death Note:
  • Light Yagami goes insane by the second episode yet still manages to blend in with society. By the end of the series, he's defeated and everyone figures out just how crazy he was.
  • Mikami also counts. There are quite a few scenes in which you see him completely calm, and controlled... until you see just how crazy he is in the warehouse scene.
• Subverted with Yuno from Future Diary. At first, she seems like an ordinary teenage girl, and perfectly innocent... except that she really isn't that. Then the series starts showing her actual thought process by the end, and it turns out that the initial impression was basically correct; Yuno is just what happens when an ordinary, innocent teenage girl sees some serious shit and tries to unfuck the situation by going full Kyle Reese.
• Ryouko Asakura from Haruhi Suzumiya seems like a calm, kind student, but follows a brand of Blue-and-Orange Morality that from a human perspective is utterly insane.
• Attack on Titan has Reiner Braun. Considered by the others to be stable and reliable, he's actually the least mentally stable of The Moles, although at least part of this is that he's so mentally broken that he completely forgets that he's actually a spy and that his cover isn't his real life.
• Mami Tomoe from Puella Magi Madoka Magica is a tragic example. Her selfish wish to save her own life at the cost of forgetting her parents made her feel incredibly guilty; to atone, she decided to fight the witches and clear off her sin by saving as many lives as possible. Of course, as a teenager who risks her life every day, she's often afraid, depressed and lonely but has created the image of a flawless, elegant and matured Cool Big Sis. She eventually becomes a mentor and Cool Big Sis to the other Magical Girls. However, in the third known timeline, when she found out the truth of Magical Girls eventually turning into witches like Sayaka had done before, she went completely berserk, Mercy Killing the other girls with the intent to commit suicide. She succeeds with Kyoko, but Homura is saved by Madoka killing Mami. After this event, Homura discovered that Mami's mental stability is probably the worst, and from then on dissociates herself from her.
• Mobile Suit Gundam SEED has Rau le Creuset, who throughout the series seems to be a calm, efficient Reasonable Authority Figure who just happens to be working for the bad guys. This made the revelation of how seriously twisted he really is all the more shocking when he started ranting and raving in front of Kira and Mu. And then he goes right back to being calm and collected in public after said confrontation. Bonus points for actually wearing a mask all the time, and it only comes off when he's at the height of his crazy episode.
• Gendo Ikari from Neon Genesis Evangelion is ostensibly the leader of the heroic organization fighting to prevent The End of the World as We Know It. The truth of the matter is far more complicated, as he's plotting to cause it instead in a mad quest to be reunited with his long-dead wife.
• Dragon Ball:
  • While he's able to hide beneath a polite and suave act and function well enough to run a business, beneath it all, Freeza is a brutally sadistic, Ax-Crazy psychopath who will kill anyone, even his own minions, For the Evulz, and the mask falls off completely when Goku defeats him. In Dragon Ball Z: Resurrection 'F' and Dragon Ball Super, he suffers from Sanity Slippage from his time in Hell, and his humiliating defeat to Goku and his death at the hands of Future Trunks, and while he tries to hide it under his usual polite façade, the mask is considerably more transparent.
  • When Goku Black first appears in Dragon Ball Super, he doesn't talk and just kills everything in sight. When we finally see his form, he grins and tells Future Trunks how he was finally going to kill him, while still remaining calm and polite. It's in the second episode that we get hints that Black may not be completely sane, given how he laughs when Trunks punches him in the stomach. In episode 51, when Black tells Trunks why he's killing humans, it's confirmed that he isn't really sane, especially with all his mood swings.
  • While Future Zamasu mostly acts calm and confident, it's obvious by his Slasher Smiles and Motive Rants that he fell off the deep end a long time ago.
• Ghetsis Harmonia in Pokémon Adventures shows a kindly, smiling face and polite demeanor at all times even as it becomes increasingly obvious that he's a psychotic megalomaniac who won't hesitate to do horrible things in pursuit of his goals. At the end of the Black 2/White 2 arc, this mask shatters and he exposes how insane he truly is.
• Saiou/Sartorius in Yu-Gi-Oh! GX. For the most part, he remains stoic in his behaviour, without anyone possibly suspecting he is possessed by the Light of Destruction, until the Light comes straight forward with its plan and duels Edo/Aster or Judai/Jaden, behaving like a maniac in the process.
• Texhnolyze: Whenever Kano speaks, his words are ever cool and quiet, but it's made emphatically clear that saying Kano is fucked in the head is akin to saying that Lux isn't a holiday resort.
• Tokyo Ghoul has quite a few characters who turn out to be masking a deranged mind.
  • Ken Kaneki masks his enormous psychological issues behind a meek, shy personality. It isn't until he's forced to confront his own damaged mind that it begins to become clear just how unstable he really is. He's prone to hallucinating conversations with people alive or dead, suffers Trauma-Induced Amnesia, and is deeply suicidal at various points. His insanity is at it's worst during his tenure as the "Black Reaper", masking his fracturing psyche beneath an intimidating and cold mask.
  • Dr. Akihiro Kanou seems to be a very polite, fatherly surgeon with a kind bedside manner. He maintains this same fatherly behavior when he's explaining how he is Above Good and Evil, leaving his "daughters" to die, or taking an electric saw to a test subject's insides. He isn't insane or a sadist, his genius is merely not appreciated or understood by society.
  • In a shocking twist, Tooru Mutsuki is discovered to be repressing memories from several horrifyingly violent incidents. After being forced to confront his own damaged mind, he has a complete psychotic breakdown. In the following month, he begins hiding his newly awakened sadistic urges by pretending that everything is still normal. A few others pick up on something being wrong but can't quite figure it out.
• Sword Art Online:
  • Nobuyuki Sugou pretends to be a friendly, stable guy, and the act is convincing enough to completely fool Asuna's parents, who set him up in an Arranged Marriage with their daughter. Beneath it all, he's a totally sadistic, Ax-Crazy Jerkass prone to Evil Laughs and Slasher Smiles, especially in his role as Oberon in ALO. Once Kirito defeats him, the mask comes off, and he's arrested and incarcerated.
  • Downplayed with PoH. He's always been a murderous psycho, but he's a low-functioning sociopath who can pass himself off as a high-functioning one.
    A cold gust of wind rustled his leather hood, revealing the eyes underneath for a brief moment. They were red and dimly glowing. A devil. He was not human, but a true devil. That was the true nature of PoH. The mask of the cheerful agitator he wore in Aincrad and the mask of the harsh commander he wore here were both just that: lies. In truth, he was a cold, cruel agent of vengeance who sought only to inflict pain, to torment and wipe out all traces of humanity...
  • Quinella hides her domineering and selfish nature behind a façade that is convincing enough to garner much good publicity.
  • Gabriel Miller comes off as cold and professional, but as the story arc continues, it becomes clear that he is a batshit insane megalomaniac who's completely psychotic.
• Shinobu Sensui from YuYu Hakusho. Oh, sure, once he rears his head in earnest, for the first five minutes or so, he seems like he's on the even-keel and in control of his actions. Then he starts cackling like a madman, his vocabulary regresses and he starts oscillating between calm efficiency and boisterous posturing; all of this on the heels of a plan so balanced between nuance and flexibility it could be furthered by its conspirators' successes or defeats.
• Masaki Meguro from Kengan Ashura is a deranged psychopath who delights in murder and has killed his own father and the other members of his dojo when he's just 13. However, he managed to spend the years before that pretending to be just a talented yet humble young man. Omega introduces us to his brother/clone, Masaki Hayami, who is introduced as a Nice Guy who gets along well with other people, but when he gets on the ring, he proves to be just as deranged as his predecessor.
• A variant happens in Muhyo and Roji. While the more benign ghosts have trouble communicating with the few living individuals who can see them, the ones who can communicate articulately and appear friendly are the psychotic and murderous kind of ghost.

Comic Books

• It's occasionally implied that Batman isn't as sane as he appears to be, what with jumping around rooftops as The Cowl and all, albeit mostly in the form of sarcastic jokes at his expense — his parents' deaths still haunt him pretty badly.
• New Gods: While Darkseid is well-known as one of the most cunning and stoic villains in The DCU, he really is just as Ax-Crazy as all of his minions. He just manages to hide it all due to extreme self-control. His son, Orion, who was raised to be heroic isn't quite as good about his dad at hiding it and it has the effect of just making him an asshole.
• Spider-Man: Anyone who takes the Goblin formula is driven completely insane, but they can still act perfectly sane when they need to.
• The Transformers (Marvel): In the UK stories, Galvatron initially acts relatively calm and reasonable, horrific pointless cruelty aside, but as Target: 2006 goes on, the mask starts gradually slipping, until he finally loses his cool altogether.
• The Boys:
  • The Homelander is a charming Captain Patriotic while the cameras are rolling, but a hedonistic Manchild the rest of the time, like all of the other supers. However, we soon see that even that is a mask hiding the raving lunatic within who commits atrocities like raping women and eating babies. But then it turns out that the insanity was pushed on him by his clone who wanted him to finally snap in public so that he (the clone) could kill him as he'd been designed to.
  • The clone himself has an easier time disguising his utterly inhuman disregard for life since as Black Noir, he never speaks or shows emotion.
• The Transformers: More than Meets the Eye:
  • Tarn of the Decepticon Justice Division positions himself as an educated sort of a bot, insists that everything he does is a reluctant necessity, tells himself that Even Evil Has Standards, and otherwise acts like a simple bureaucrat who happens to be tasked with torturing and murdering Decepticon deserters and whose only actual quirk is an addiction to transforming. As his Villainous Breakdown unfolds and he brutally murders one of the underlings he was previously very protective of for "going soft", it becomes increasingly clear that at heart, he's a sadistic, violent whack job and may well be the most viciously unstable member of the DJD. For bonus points, he wears the Decepticon symbol as a literal mask.
  • Getaway at first presents as a likeable, quirky friendly guy who got on well with Skids and snarks amusingly about the eccentricities of the Lost Light crew. As time goes on, all of this is revealed to be an act: deep down, he's a ruthless, predatory manipulator with an elaborate cocktail of personal issues and a mile-wide streak of pettiness and cruelty, totally obsessed with claiming his "destiny" as a Prime, indifferent to the death and suffering he either actively causes or does nothing to prevent.
    Froid: He makes for a fascinating case study. Narcissism, impostor syndrome, a truly multi-faceted inferiority complex...it's quite the cocktail.

Fan Works

• Inverted in Abraxas (Hrodvitnon). Nadezhda notes in Chapter 11 that the Basement Club still acted somewhat normal, compared to the others who suffered Sanity Slippage from the decapitated Ghidorah head's psychic influence, but it was easy to spot that just below their surfaces something was seriously wrong in them.

• Rosario Vampire: Brightest Darkness Acts III and IV have a perfect example in Hokuto Kaneshiro. While he constantly acts polite and sane, and even manages to win the trust of Tsukune's group, it's revealed that he himself personally arranged for Kuyou to attack the academy so he could steal an Artifact of Doom while the gang was distracted fighting him, needing said artifact to revive Alucard and destroy the world out of the nihilistic view that all live is evil and meaningless. Also, when his Co-Dragons, Jovian and Jacqueline Kikion, are resummoned in Act VI, they state that their morality is shaped by their master; when one considers that Jovian and Jacqueline were Ax-Crazy Psychopathic Manchildren who committed such atrocities as rape, Cold-Blooded Torture, and wanton mass murder and destruction as a matter of course, it's even more proof of just how off his rocker Hokuto really was.
• As The Rise of Darth Vulcan goes on, it becomes increasingly apparent that the titular Villain Protagonist is wearing one. Ted/Darth Vulcan spent years suppressing his true nature and acted like a jerk in order to avoid bullying, to the point that even he forgot what he was really like, leaving him deeply disturbed. This is why he's at first seemingly immune to the Sanity Slippage-inducing effects of the Alicorn Amulet — it can't drive him insane, because he was never sane to begin with.
• In Digimon Adventure 02: The Story We Never Told, Oikawa spends his first few appearances as a coldly calm and slightly sinister Mysterious Watcher. Once he reveals himself as The Man Behind the Man, however, it quickly becomes apparent that he is a highly unstable Psychopathic Manchild prone to bouts of sudden shouting and raving about his megalomaniacal world view.
• Child of the Storm: General Lukin, one of the Arc Villains of the sequel Ghosts of the Past, at first appears to be a sociopathic yet calm and controlled General Ripper. However, as he gains more power, it becomes more and more clear that he's utterly insane and bloodthirsty, and he stops trying to hide it. When things turn against him, he has a Villainous Breakdown and becomes a gibbering madman.
• CRME: Cinder Fall usually comes across as an elegant young woman, but even in the show RWBY, under this was a sadistic, power-hungry egomaniac. This fic pushes this further by showing that her current composed disposition is something she had to learn. In private, her mask slips often showing that she's borderline Ax-Crazy.
• Code Geass Megiddo: The revelation that Suzaku Kururugi has been wearing one isn't much of a surprise. After the death of the woman he loved, the tarnishing of her good name, and then being forced to play best friend to the amnesiac ex-best friend that was responsible for all of that for eight years, his insanity, while tragic, is not entirely unexpected. What is unexpected is how long the mask has been in place. He had it on years before he even met Euphie, after he murdered his father to save Lelouch and Nunnally. All of the above just made what he was hiding worse.
• In Loved and Lost, Prince Jewelius initially plays a sane nice guy quite convincingly. While he acts more arrogantly after he takes over Equestria's throne, he's sure to give the manipulated public and Twilight Sparkle superficially sound logical arguments to justify his harsh decisions. However, once he starts losing his control over everything, he stops caring about hiding his true nature as a spiteful sociopath driven by jealousy towards royal family members who have done nothing to deserve his cruelty.
• In Mauling Snarks, a Worm fanfic, the PRT officer that manipulated Taylor and Amy into executing a kill order is completely nuts, but fully leans on his power to manipulate paperwork to pass psych evaluations and appear completely sane. Once Hatchet Face nullifies his power, he becomes a gibbering mess.
• RainbowDoubleDash's Lunaverse: Midnight at first seems like a dull and slightly jerky bureaucrat, who may or may not be under mind-control, until they get hit with a spell noted to have unfortunate side-effects on the less-than-sane. Trixie and Berry Punch are shown to get away with nothing more than nasty headaches. Midnight goes berserk.

Films — Animation

• The Lion King (1994): In the first part, Scar is able to cover his sociopathic nature beneath a charming veneer; not that it completely hides his cruelty, but the other lions (his brother Mufasa included) just assume that he is an ineffectual Jerkass at worst. Once things start going awry, he undergoes a severe Sanity Slippage; witness his refusal to face up to the reality that the pride needs to move, even though he himself will starve to death otherwise.

Films — Live-Action

• In Apartment Zero, Jack appears to be perfectly normal. Even when he is implied to have killed someone, he remains perfectly calm... and then Adrian walks in on him with a body, and we see just how crazy he truly is.
• Asylum (1972 Horror) has three examples:
  • At first, Barbara appears to be the sanest of the patients seen yet, demanding that she see her lawyer and insisting that Dr. Martin can see that she's "not ill". The only hint of madness is her insistence that what happened was not her fault, it was Lucy's, which gives the viewer an indication of what her story is going to be like. However, it's the end of her story that conclusively shows her insanity, as she points out 'Lucy' in her own reflection before laughing madly.
  • Byron is also quite composed when he meets Martin, even acknowledging that his goal of bringing his toy robots to life sounds far-fetched. However, when Martin starts to leave, Byron realizes that Martin considers him insane and starts ranting about how he'll prove that he's right. After he succeeds in animating the robot modeled after himself, he shows himself to be murderous as well as mad, as he sends it to murder Dr. Rutherford.
  • Dr. Starr is ultimately revealed to be none of the patients seen. He's actually Max the orderly — or rather, he murdered the real Max and took his identity. Not even a trained psychiatrist like Martin realizes that that 'Max' is a homicidal maniac, and the mask only slips after Starr has killed Martin, whereupon he too starts laughing madly.
• Batman (1989): Even before the chemical dip that turned him into the Joker, it's heavily implied that Jack Napier was always Ax-Crazy, hiding it under a professional mobster persona that occasionally slipped up when someone called him crazy; Bruce reviews Napier's criminal records and discovers he was a psycho with a "head full of bad wiring" before he even made it to junior high. If anything, the chemical bath didn't really break his mind as much as it just set Joker's impulses free.
• Bird Box: Gary effectively hides his true nature as one of the crazy survivors until the group at the house is distracted by Malorie and Olympia going into labor, allowing him to catch them off-guard.
• In The Dead Center, the previously catatonic psych ward patient John Doe suddenly regains his memory and awareness, and demands to see his kids. His real name was Michael Clark, but his body was taken over by the demon who is now pretending to be Michael, to get him out of the psych ward quickly.
• Godzilla: King of the Monsters (2019): Though some, including Mark, were concerned about Emma Russell's initial Workaholic response to losing a loved one, during the film she successfully masks her Sanity Slippage from all of her Monarch colleagues. Before the film's events, even her own daughter is unaware just how messed up her mother really is despite remaining in her custody and being recruited into Emma's Eco-Terrorist agenda.
• Guardians of the Galaxy Vol. 3: The High Evolutionary presents himself as a ruthless but well-meaning scientist whose goal is to create a perfect world. The movie repeatedly shows that under that veneer, he's a petty, vindictive, cruel, selfish asshole with a wildly out-of-control God complex and a Hair-Trigger Temper, his vision of perfection is forever going to be unreachable due to his ego, and his fixation on Rocket is driven less by a desire to see why his brain is unique and more by vengeful spite. By the time he's blowing up his own ship while standing on it without any kind of exit strategy, solely to kill the Guardians, his own underlings conclude that he's totally lost it and pull guns on him; he murders them all instantly, but points for trying.
• In The House That Jack Built, the titular Villain Protagonist at one point admits to Verge that he probably is a psychopath, noting that he never really felt or understood the concept of empathy, and he had to spend a lot of time learning how to fake it in order to better fit in with normal society. As he explains this, a montage of Jack practising various facial expressions in a mirror plays.
• In Nobody, Hutch is introduced as a quiet suburbanite who comes across as bored and boring. It's soon revealed he's a former assassin with a tendency towards extreme violence who wanted to try living a normal life. He genuinely does love his family but he also really, really wants to beat the shit out of some people.
• Scream (1996): The Ghostface killer (well, killers) appear perfectly sane, if odd, until the big reveal at the end. Billy is better at keeping the mask on than Stu is, which makes him all the more creepy when The Reveal comes.
• Kylo Ren from the Star Wars sequel trilogy has this, both figuratively and literally. As he is something of a Darth Vader fanboy, he tries to project a calm, menacing image just like his idol. But he is prone to explosions of temper when things don't go his way, often destroying machinery and/or harming his subordinates when this happens.
• Who Framed Roger Rabbit. Throughout the film, Judge Doom appears somewhat malevolent, but not blatantly so. Near the end, he's revealed to be a Toon who's even more crazy than most.

Literature

• Parodied in American Psycho. Patrick Bateman is an Ax-Crazy Serial Killer working on Wall Street. He constantly tries to confess the murders that he has committed, but no one takes him seriously. Finally, he flips out completely and does everything in his power to get caught... and still no one cares.
• The murderer in And Then There Were None is a calm, rational person in public, but an Ax-Crazy Large Ham once he arrives to kill the last victim in most adaptations. The original story is a subversion, however; there the murderer manages to keep a lid on his mania throughout the story, and only allows himself to rant through his suicide note explaining the whole sequence of events.
• Battle Royale: Kiriyama sits quietly in the background, but starts killing students mercilessly once the game starts — in the movie, it turns out that he signed up for the Program.
• In Breakfast of Champions, after Dwayne Hoover goes on his rampage, people say afterwards they should have seen the danger signals in his behavior, but the narrator then points out that this "cry for help" was only obvious in retrospect: Dwayne's behavior prior to meeting Kilgore Trout had been within the bounds of normally acceptable behavior, and his closest companion and mistress at the time, Francine Pefko, had thought that he had been getting happier.
• The androids in Do Androids Dream of Electric Sheep? are capable of human and super-human cognition but supposedly have no human emotions and are incapable of empathy, the core value in Mercerism. According to this view, widely held in human society, any displays of emotion by an android are faked in order to manipulate humans. However, it's ambiguous whether this is actually true. Irmgard Baty clearly shows an emotional response to Isidore freaking out over the dead spider, and attempts to comfort him — because we are not given her internal monologue, her reaction can be interpreted in multiple ways, raising the question of whether a distinction can be made between "artificial" and "genuine" emotion.
• Mass Effect Annihilation: The person responsible for the virus. Worst is that it's the captain of the quarian Ark, who everyone thinks is a charismatic, All-Loving Hero, but is rabidly xenoist towards pretty much all the Council Races and completely insane. When she's found out, she's even asked how she managed to get past the supposed psychological screenings the Andromeda Initiative was supposed to have — she just figured out how to lie her way through the tests.
• Neverwhere: The Big Bad, Islington, is pleasant, personable, and reasonable, with all the decorum one would expect of an angel — until they're challenged about their culpability for the fall of Atlantis, and the façade cracks for an instant:
  It was as if the lid had been pulled off something dark and writhing: a place of derangement and fury and utter viciousness; and, in a time of scary things, it was the most frightening thing Richard had seen.
• A Song of Ice and Fire:
  • Roose Bolton first appears to be merely cold and ruthless. However, he is actually almost as insane as his torture-loving bastard son, Ramsay. He's just smart enough to avert his son's Stupid Evil behavior and only indulges himself when he's sure that it won't come back to bite him.
  • In spite of being a seemingly-charming cheeky chap, Petyr "Littlefinger" Baelish is a ruthless homicidal sociopath underneath it.
• In The Stormlight Archive, Nale, who goes around killing prospective Radiants under the belief that this would save the world. As Edgedancer shows, most of the time he seems perfectly normal, if a tad obsessed with formalities and documentation, but whenever a crime is committed in his vicinity, he turns into a murderous monster you can't reason with.

Live-Action TV

• Cobra Kai: Terry Silver puts on a rather convincing polite and gentlemanly veneer as a mask to his manipulative and bombastic tendencies, and it's made even more apparent that Silver himself had hellish experiences during the Vietnam War, coupled with substance abuse that he used as a coping mechanism for his PTSD that turned him into the raving lunatic he once was during The Karate Kid Part III. When he is reintroduced in season 4, the mask slowly slips as his then-former friend John Kreese brought him back to the dojo and at the same time being pushed to his limits by Kreese himself, leading to their betrayal. In season 5, Silver maintains that same veneer in terms of being a Reasonable Authority Figure as a sensei and/or a Villain with Good Publicity in general. He has no problem dropping the act if he's agitated enough, as Daniel found out the hard way in their first fight.
• Game of Thrones:
  • Roose shares his son's sadism. He's just a lot better at hiding it.
  • Ramsay is rather calm, polite, and approachable when pretending to be Theon's savior, though there is something subtly strange about his forced mannerisms and speech pattern.
• House of the Dragon: Queen Alicent seems like she lives up to her role as Queen, but her sanity is on a downwards spiral ever since her Best Friend Rhaenyra Targaryen lied to her about her affairs and she reaches a boiling point when Rhaenyra's son Lucerys blinds her son Aemond in one eye and she asks "an eye for an eye" in a very literal sense.
• In Gotham, the identical twins who end up being the Batman prequel show's two main takes on the Joker are both good at convincing everybody around them that they are harmless. In the first season, when Jerome is introduced, (almost) no one at the circus seems to suspect that he was the one who killed his mother, despite the fact that later episodes make it clear that her abuse of Jerome was so extreme and frequent that it would have been an open secret in the circus. He is also able to convince Jim Gordon that he is genuinely grieving his mother, despite the fact that Gordon is a seasoned detective, and Jerome hates his mother so much that he laughs when he confesses to killing her. Jeremiah is able to convince Bruce, someone whom he considers his best friend, and who will someday be recognized as the World's Greatest Detective, that he is perfectly fine, despite the fact that he has been driven insane by Jerome's insanity toxin and is plotting to turn their clean energy generators into powerful bombs.
• Kamen Rider Wizard: While it's no surprise that all of the phantoms are insane, special props goes to Sora/Gremlin. Before The Reveal, we see that he is a giggling little troll. He's obviously dangerous and even manhandles Wizard and Beast a couple times, but that's barely the surface. He then reveals that he is the only phantom to retain his human persona, that's when the real reveal begins. The people who knew him before the Sabbath say he was a nice, if eccentric, guy. It turns out that he's a Serial Killer who continues this as a hobby.
• Post-snap Dukat in Star Trek: Deep Space Nine manages to hold it together fairly well for about half of "Waltz", only reacting to the hallucinations when he's safely away from Sisko. This does not last.
• Arrow: Slade Wilson spends most of his post-Face–Heel Turn appearances in Season 2 as a seemingly coldly detached and stoic Magnificent Bastard who keeps his calm even when fighting Oliver. However, near the end of the season, the mask comes off, and he reveals how deranged the Mirakuru has left him, in all his ranting, hallucinating glory.
• Hannibal Lecter is one of the most famous psychopaths in fiction and is almost always portrayed as getting away with his crimes for many years because of his almost flawless mask, but Hannibal shows several occasions when the mask slips a bit and his real nature shines through. Usually only the audience sees this, but on one occasion his psychologist Bedelia comments on this and describes Hannibal as wearing "a person suit" that fools most people but not her.
• Legion from Red Dwarf is initially calm and pleasant. After the truth comes out, he also admits that he's a gestalt entity made from whoever is on the station at the time, and while he's got the gang's good qualities, he's also got their malice and neuroses, "magnified many times". Fittingly, this reveal comes after his literal mask is knocked off, revealing his Nightmare Face.
• The Walking Dead (2010): In the episode "Here's Not Here", Eastman shares a story with Morgan about a prisoner he interviewed. The prisoner was a model inmate up for parole until Eastman interviewed him and realized he was a psychopath. The prisoner, realizing Eastman was on to him, immediately tried to kill him. See the Quotes page for more detail.
  "And I — and I saw his face, his — his eyes, his evil. Mask had slipped. And he was gonna kill me right then and there because he knew I would make sure he would never get out again."
• Homicide: Life on the Street: In "Subway", the killer initially seems like a normal guy when Bayliss and Pembleton interview him. When Bayliss determines he's the killer, he drops the face and reveals himself to be a barely lucid Psychopathic Manchild.

Music

• Children of Bodom's "Mask of Sanity" is a song about a person who's at least trying to "keep his mask on":
  Daylight's sin inside, day's growing closer, wait for pain
  I cannot wait another night to be alone
• Kanye West's first verse from the song "Monster" references this:
  Bought the chain that always give me back pain
  Fucking up my money so yeah I had to act sane

Tabletop Games

• Call of Cthulhu:
  • Cultists with a Sanity of zero usually act in a completely insane or otherwise irrational manner. However, powerful cultists (such as the leaders) are usually able to act in a sane manner when dealing with sane (normal) people in order to conceal their true nature.
  • The related game Trail of Cthulhu explains this by separating Stability from Sanity. People with little Stability are prone to panicking and fainting and such, but may still retain a good grip of their Sanity. People with high Stability and low Sanity, on the other hand, embody this trope.
• Hunter: The Vigil supplement book Slashers, which focuses on serial killers and similar psychopaths, gives us Charmers, a category of slashers who specialize in killing people by winning their trust, meaning they specialize in giving other people the illusion they are sane, perfectly nice people. This is only a mask however, and anyone who manages to see through their acts and refuses to trust them is very likely to cause them to lose their cool, breaking their mask.
• This trope is more or less what the Piety stat from the fan-made game Leviathan: The Tempest represents in a Leviathan's cultists. At low Piety, the cultists are still capable of functioning in their day-to-day lives, but when they're interacting with or actually doing tasks for their Leviathan they degenerate into raving loons who, if asked to apply for a mortgage on behalf of a Leviathan, would turn up in ceremonial robes and declare how blessed the bank must be to have an opportunity to serve. At higher Piety, the cultists are still crazy, but they are capable of faking sanity well enough to run errands for their god and in various ways work society and the legal system to advance his goals.
• Princess: The Hopeful: In another fan-made game, this is a large part of the danger posed by the Mnemosynes and Cataphractoi. Unlike the more common and bestial Darkspawn, both are capable of mimicking humanity well enough to interact with society, making them far harder to detect and allowing them to use mortal institutions to their advantage.
• Magic: The Gathering:
  • Geralf Cecani is, in his own way, just as childish, petty, short-tempered, obsessive, and eccentric as his sister Gisa, but he tries to act more intellectual and rational about their endless, pointless pissing match over how to best build zombies.
  • Elesh Norn puts on a veneer of perfect calm as the Mother of Machines. It starts to crack as she goes after some of her own minions for growing outside of her ideas for them and eventually shatters entirely, revealing the self-obsessed egomaniac underneath, when Elspeth starts coming after her.

Theatre

• This is one interpretation of the title character's actions in Hamlet.

Video Games

• Naufragar: Crimson: Hyo is normally good at impersonating Kyo's mild-mannered personality and manages to fool Jarret, who is a close friend of Kyo. However, he's murderously insane underneath the act and at one point threatens a man who seemed like he knew Anastasia.
• Uncharted 4: A Thief's End: While he's able to put up a respectable and calm act, even at his best, Rafe Adler is an Ax-Crazy bastard who can snap at a moment's notice. Best shown at the criminal auction; while he greets Sully calmly at first, within minutes, he snaps, slaps Sully's drink out of his hand, and openly threatens to send him home in a body bag in front of an entire crowd of witnesses; Nadine just barely manages to pull him back in.
• Evil Genius: The Butcher (a cannibalistic, cleaver-wielding psychotic ex-medical student-turned henchman) can temporarily fool Investigators with his first skill called 'Façade of Normality', which renders him less suspicious and even able to pass for a sane person, as opposed to instantly alerting them due to his violent insanity.
• Zanara Capella from Capella's Promise was crazy since he tried to stitch together a fish and a frog as a child, but he managed to hide his mentality long enough to succeed his father as king. Even when his goal of becoming a god to give and take life is revealed, he manages to sound very regal throughout his Motive Rant and never drops this façade until his plans fall apart.
• Forever Home has the Big Bad, General Barclyss. On the outside, he seems like a professional and cold officer who remains calm even as he orders the slaughter of countless innocents and butchers POWs into mangled corpses. After most of his army is decimated and it looks like he's about to lose for the first time, the mask comes off completely and reveals him for his true Ax-Crazy self. He ends up slaughtering most of the engineers when they so much as question him and by the time the party reaches him for the final battle, he's ranting and raving about how he finds life meaningless, all while threatening to launch a huge explosive rock at the planet if no one can give him a satisfactory answer as to why they want to live.
• BlazBlue:
  • Hazama is an odd example — considering how often he laughs maniacally, you'd be surprised how calm and stable he can appear.
  • In BlazBlue: Central Fiction, it turns out that the calm and professional persona employed by Hibiki Kohaku is actually a façade that hides his true nature: a deeply-disturbed individual who desires to be the perfect killer, which he wants to achieve by assassinating his boss, Kagura.
• A Malkavian character in Vampire: The Masquerade - Bloodlines ingeniously hides their Split Personality by pretending to be twins, namely, Theresa and Jeanette Voermann. However, this has extra levels: normal people wouldn't be surprised if an owner/manager of a place called "The Asylum" was professionally acting a little crazy, and people looking for a Malkavian will find the actual insanity hidden just well enough to go out in public that they'd be expecting — this example manages to layer apparent Obfuscating Insanity under Mask of Sanity under more accidental Obfuscating Insanity.
• The Legend of Zelda:
  • Zant from The Legend of Zelda: Twilight Princess. He seems like a calm, cold, mildly angry villain throughout the whole game. But before you fight him he takes off his mask as well as his controlled demeanor. Cue an enraged verbal exchange with Midna, and one of the most spastically moving and sounding bosses in the franchise.
  • Ghirahim from The Legend of Zelda: Skyward Sword combines this with being Faux Affably Evil. He outwardly tries to keep an image of being an elegant, refined gentleman, but this belies some serious Mood-Swinger tendencies and a casual love of violence.
• Throughout Luigi's Mansion, King Boo was calm, collected, and in complete control. After, however, he was overtaken by sheer insanity and, while he was outwardly almost the same throughout the sequel, you could tell that behind his face was a sociopath out for revenge, no matter the cost.
• While Dutch’s true colors in the Red Dead series is left to interpretation, this is one of the In-Universe theories about his behavior. John, in particular, believes by the end of II that he was always crazy and managed one of these until things went south.
• In Shin Megami Tensei: Strange Journey, in the Law Path, after Zelenin has brainwashed all Red Sprite personnel, Dent assumes the role of the Only Sane Man and keeps issuing EX Missions. Finish all missions, and Dent sighs contently — everyone is happy — happier? He then proceeds to rip off his Mask of Sanity and stomp on it by groveling and addressing you as "Master".
• The Traitor in Persona 5 acts calm, polite and affable in everyday life, but hides an Ax-Crazy side that comes out in full force during their boss fight. Added events in Royal, where they join the party as a Token Evil Teammate, make it clear this murderous side is their true personality.
• Dr. Eggman Nega of the Sonic the Hedgehog series comes off as a calm, well-mannered, gentlemanly individual, but when push comes to shove proves to be a complete psychopath who delights in destruction and the suffering of others.
• This happens quite often in the Ace Attorney series. Most of the culprits will start off faking innocence or serenity, only to have an inevitable breakdown after the player pokes enough holes in their testimony.
  • In Phoenix Wright: Ace Attorney – Justice For All, Matt Engarde is able to fake being stable enough to be a famous actor and trick Phoenix into thinking that he's an innocent, lovable ditz. It turns out that he really lacks any empathy, being perfectly fine with hiring an assassin to kill his rival actor and letting said assassin blackmail Phoenix into defending him via kidnapping Maya. He also seems to completely believe that he's innocent, since he hired an assassin and didn't commit the murder himself.
  • In Phoenix Wright: Ace Attorney – Trials and Tribulations, Dahlia Hawthorne is heavily implied to be a sociopath, stating that she has never done a single thing for the benefit of anyone besides herself. She's easily able to pass herself off as a vulnerable victim in need of protection and is even able to disguise herself for some time as her much-saner twin sister.
  • Apollo Justice: Ace Attorney: Kristoph Gavin gets through their first trial with the mask still on, appearing for all the world to be The Stoic whose only response to their guilt being proven is to slam their fist on the witness stand. When they next appear in 4-4, you get to pull the mask off to find an unstable narcissist obsessed with being needed and unable to even acknowledge their own motives.
  • In Phoenix Wright: Ace Attorney – Dual Destinies, the phantom is an utterly remorseless killer who claims to have trained himself not to feel emotion at all. He seems eerily detached from the many killings he does. He is also able to fake having emotions perfectly, as it's revealed when Phoenix discovers that he'd been perfectly masquerading as the incredibly emotional Detective Bobby Fulbright.
• Nagito Komaeda from Danganronpa 2: Goodbye Despair appears to be sane, until halfway through the first trial, when it's revealed that he's completely insane about hope, going so far as to attempt to murder somebody to preserve it.
• Yandere Simulator:
  • Word of God says that the Sanity Meter is somewhat of a misnomer, since Ayano has always had something wrong with her. In reality, it's a measure of how well she can keep the mask on. If her Sanity is high, she will be able to interact with her schoolmates as normal. The lower it gets, the more 'off' she becomes, and when it's completely slipped (33% or below Sanity), she'll have Empty Eyes, a shadowed face, and a prominent twitch. The game screen will become smudged and desaturated, she'll constantly hallucinate killing her current rival, she will no longer perceive students other than Senpai as anything but silhouettes, she'll giggle uncontrollably, and she will no longer be able to interact in any manner other than murder. Let Senpai see you like this, and it's an instant game over for you.
  • Snap Mode, which is accessed after you get a game over, shows what happens when Ayano drops the mask entirely. It's... not pretty at all, as she goes on a rampage killing anyone she gets near with her bare hands in her quest to kill Senpai and then herself.
  • A video detailing Ayano's backstory reveals that she's been keeping this up for ages. Even as a child, she never felt any kind of emotion, except pity for her parents who were trying so hard to make her happy, and some mild frustration when she was bullied at school. So she put on a happy face while still feeling empty inside, which both pleased her parents and stopped the bullying. Even though she still doesn't care about anyone else (except for Senpai), Ayano admits that wearing the mask makes life more convenient for her.
• Hyness from Kirby Star Allies first seems to be a very calm, cold, and truly evil character, especially shown when he shoves his most loyal follower after she begs him for help. Just before his fight, he makes a very fast speech telling his goals, which could raise a few eyebrows, but nothing that bad. During the first phase of his fight, he mostly just tosses dark orbs at you. However, when you beat him for the first time and knock off his cloak, he reveals how insane he truly is. After draining three of his followers, he starts attacking more randomly and is much faster, and he uses his followers' unconscious bodies to bludgeon you. After you beat him again, he mind-controls the three followers into powering up the Artifact of Doom, before jumping in himself.
• This happens in the Shadow Hearts series for some of the people who read the Émigré Manuscript. Most go Laughing Mad, but the ones who get to the level of Mask of Sanity, are the ones who have unlocked its true power. In the first game, once endgame is reached, it is painfully clear how off his nut the Big Bad has apparently been even back when he seemed like a sophisticated gentlemen.
• In Fire Emblem: Three Houses, Dimitri is introduced as a chivalrous young man, but his kindness hides a severe vengeful streak that borders on Ax-Crazy at his worst. He spends most of the first half of the game trying to suppress his dark side, but after the events of the Wham Episode and the five-year timeskip he's lost the mask and become openly obsessed with taking revenge to the exclusion of all else (even his own kingdom). Ironically, he's the least unhinged — if only by a rather narrow margin and mostly thanks to Rhea's presence — in the route where Byleth (read: the player) backs his sworn Arch-Enemy, the Flame Emperor (a.k.a. Edelgard).
• In Final Fantasy VII, the main character, Cloud Strife, has been wearing a mask based on the memories of his deceased friend Zack Fair through the Jenova cells for years. When the mask finally breaks, he's left a mental wreck who is completely catatonic.
• In Saiko No Sutoka, Saiko-chan wears one during Yandere Mode, where she is calm and helpful to the player... as long as they do exactly what she says, which will lead them into a trap. If not, then she starts to lob poison gas bombs at them. During the regular game, the mask is all the way off, and it isn't pretty.
• The mastermind behind the events of Psychonauts 2, Gristol Malik (a.k.a. Nick Johnsmith), may be the most rational villain in the games so far, but his mental world quickly shows it is definitely not the same thing as being sane — Fatherland Follies is a massive theme park ride dedicated to himself, there's essentially no depth to the mindscape at all, and his ego is shown regularly riding it to bask in his family's glories. He was able to hide this utter narcissism behind a Nice Guy facade for years.
• The "Boring Cop" Copotype in Disco Elysium is the Detective's attempt to build this. Downplayed in that the Detective isn't malevolent, just a mess of a cop. His brain is a Mind Hive of arguing personalities, and he routinely has Helpful Hallucinations, in addition to being an alcoholic (possibly recovering, depending on player choices) with severe mental issues and emotional imbalances. If he does his best to act the part of a Consummate Professional despite all this... he'll have mixed results at best. His partner will see right through it, and sometimes he'll insist a little too strenuously that he's definitely normal, sane, and boring, but those who haven't been exposed to the Detective's unique brand of weird for any length of time might actually think he's a fairly normal cop.
• Injustice: Gods Among Us: After he was tricked by The Joker into killing Lois and nuking Metropolis in an alternate dimension, Regime Superman frequently attempts to hide how far gone he is, but everybody knows he's a former shell of the man they once revered. It doesn't take long for everything to come down when he kills Shazam and Lex Luthor just for questioning his increasingly authoritarian rule. Regime Supes even threatens to destroy Metropolis and Gotham, and invade the Multiverse when people revolt against his rule.
• Shadowrun Returns: Hong Kong: This becomes a discussed trope if you engage Racter in conversation for any length of time. Racter is a sociopath and doesn't 'get' humanity, but was taught during his upbringing that pretending to be normal was the best way of getting what he wanted out of society (being put in a mental hospital in a collapsing, post-Eurowar Russia helped motivate him). An advantage to his current job as a professional Shadowrunner is that he doesn't have to bother with the mask nearly as much: A lot of his less savoury desires can be openly expressed in the Shadows and nobody cares as long as he gets the job done and sticks with his crew.
• In Trauma Team, the Raging Bomber/Sandra Lieberman can rein in her insanity to the point of appearing to be a normal deliverywoman when she delivers her bombs to the targets personally to leave no trace.

Web Animation

• RWBY: Adam Taurus outwardly projects a vibe of calm and control, in a way that inspires others to follow his lead. However, beneath this controlled mask is a violently unstable man filled with rage and described by Blake as the Anthropomorphic Personification of spite. In a private recording that he sends to the Albains, he flies into a furious rage while ordering the Belladonna family assassinated before forcibly calming himself down, complete with a hand gesture that looks like pantomiming putting on a mask. By the end of Volume 5, the mask falls off when Adam tries to blow up himself and his own followers simply so that Blake doesn't win, and everyone in the White Fang sees how evil and crazy he really is. Yang even indirectly alludes to this when she counters his claim of Blake breaking her promise to him:
  Yang: Did she make that promise to you, or to the person you were pretending to be?

Webcomics

• Snadhya'rune, the effective Big Bad of Drowtales, masterfully demonstrates this trope over the course of chapter 46 when her previous behavior where she presents herself as an enlightened peacemaker and the best hope for her kind's future shatters when her plans start going awry, culminating in a scene in which after she's surprised by a literal stab in the back she screams in utter fury and starts tearing the place down, not caring who she takes out in the process. You pretty much see the mask start to fall away and then crack completely in the course of three panels, and then several pages later she attempts to put it back on with limited success.
• Gunnerkrigg Court: Loup disguises himself as Jerrek the android. While he looks and talks like a normal person, we can see his true psychopathic personality raging in his mindspace.
• Downplayed in The Order of the Stick with Belkar, the Ax-Crazy Token Evil Teammate of the Order — the kind to butcher a random bystander who looks at him funny. During the course of the story, after getting in serious trouble and no longer getting away with his erratic and criminal behavior, he is advised by a mysterious source that if he doesn't want to become a better person, he can at least fake it for his own good — which, in keeping with the comic's Postmodernism, Belkar refers to as faked Character Development. He then keeps a low profile for a time, becoming more of a Blood Knight and focusing his murderous urges on actual threats to the Order. Later subverted when it is revealed (at least to the reader) that he actually did grow as a character and is no longer focused on killing as he used to be.

Western Animation

• Batman Beyond: In the episode "Sentries of the Last Cosmos", three youths are able to assume the roles of sentries when they meet the owner of the franchise (who is capable of making technology that gives the wearer the abilities of a sentry). He is able to convince them that the characters and events from the titular films are not fictional, but part of an ongoing galactic war that they can help win. They obey him blindly and commit several crimes. Despite being brainwashed, they draw the line when the owner of the franchise demands that they kill an obese man they'd abducted. It turns out that the man is the true creator of the franchise and he'd filed a lawsuit against the fake for taking all the credit. The fake goes toe to toe with Batman and the dialogue that follows suggests that he actually believed what he told the youths about a galactic war.
• Ben 10 has Kevin Ethan Levin. In his very first appearance, he seems to be a normal, albeit slightly more mischievous foil of Ben. As the episode progresses, it becomes clear that this isn't the case. He talks about robbing a mint in a way that would've resulted in the deaths of countless people and seems genuinely shocked when Ben refuses to help.
• Beware the Batman features Dane Lisslow, a new friend of Bruce's that wins him over with common interests, friendly nature, and overall calm demeanor. By the time he is exposed as being Slade Wilson/Deathstroke, his true nature is revealed as deranged, vengeful madman with a guttural, harsh voice.
• Castlevania (2017):
  • Carmilla makes a point of appearing calm and calculated, but when her plans go awry, she drops the façade and reveals a vicious sadist beneath. By the time of the fourth season, Carmilla's mask has disintegrated completely and her megalomania is on full display, frightening Lenore.
  • Miranda's words to Isaac are calm and collected, but she matter-of-factly admits to being totally mad and advises him to kill his enemies.
• Harley Quinn (2019):
  • Given context on Harley's childhood, it's implied that this was part of her psychologist persona as Harleen Quinzel. She was clearly very messed up as a child and teenager, but was put together and somewhat promising as a young doctor. As a result, the Joker luring her into a life of crime ends up coming across less as him corrupting her and more like he simply reawakened what was already there.
  • Batman is revealed to be this in Season 3. To other people he comes across as a collected, highly analytical person who rarely displays emotions, but the truth is that he really hasn't progressed since the night his parents died and is extremly hung up on validation from people he knows. After being dumped by Catwoman, he cracks and winds up setting off a plant-zombie apocalypse in an insane attempt to bring his parents back from the dead. Harley Quinn, for her part, is utterly horrified when she finds out how hurt he is inside.
• The Marvelous Misadventures of Flapjack: In one episode, Captain K'nuckles meets a charismatic man who is cleaner and more articulate than many of Stormalong's other residents. Flapjack discovers that the man is an escaped mental patient who believes wholeheartedly that the mole on his face gives him immortality. The episode ends with the crazed man jumping into a volcano and being burned alive, all while managing to say his catchphrase one last time.
• Milo Murphy's Law has Jackie, who seems like nothing but a big risk taker at first, but by the end of the episode everyone believes her to be insane.
• Toffee from Star vs. the Forces of Evil seems to keep extremely calm, composed, and even professional at all times. All times, that is, save for one brief moment in the Season 1 finale where he reveals his true nature and completely loses his marbles for all of a second and a half, putting on a huge, toothy Slasher Smile while gleefully yelling "SURPRISE!" after revealing his plans. He then immediately goes back to calm, collected and professional like nothing happened.
• Steven Universe:
  • At first, Eyeball seems to be the Only Sane Man of her squad of Rubies. However, "Bubbled" reveals that she's been wearing this since her introduction and when Steven heals her gem and reveals that he is the reincarnated Rose Quartz, the mask comes off and out comes a dagger as she attempts to essentially disembowel Steven by removing his gem.
  • At first, Navy seems to be as friendly and ditzy as the rest of the Ruby Squad. However, "Room for Ruby" reveals that, like Eyeball, she's been wearing this since her introduction and is revealed to be a sadistic and manipulative Bitch in Sheep's Clothing who pretended to want to live on Earth just so she could steal back her ship and only kept up the façade just to see the look on Steven's face when he realized he'd been betrayed by his "Favorite Ruby". What unsettling is that she still keeps up her cheery demeanor even after The Reveal.
  • By the time of Steven Universe: Future, Steven himself looks cheerful enough, but as the series goes on his unchecked traumas bleed through and it becomes very clear that Steven is not fine, no matter how much he tries to hide it. The mask holds until the episode titled "Everything's Fine". Steven attempts to repress the memories of his violent outbursts, trying his best to establish some kind of normalcy, even though he's grown to at least seven feet tall, glows bright pink, has gained pink eyes with diamond-shaped pupils, and is rapidly losing control of his Diamond-powers with destructive results. He stays forcibly upbeat and positive, even after he levels a building by getting too excited over a ball he caught. By the end of the episode, the Gems, Greg and Connie are staging an intervention, and Steven goes right off the deep end.
• Teenage Mutant Ninja Turtles (2012): Slash, at least in his debut episode, appears to be a smart, loyal, hardworking ninja who understands Raphael's position and his problems with his brothers. But underneath, his mind is too twisted to understand things like how no matter how frustrating families can be, that doesn't mean things would be better if they weren't around, that there are more important things in life than being strong, or that caring for others isn't a weakness. Later episodes reveal that he straightened up — from all appearances, for real.
• In Wakfu, Qilby the Traitor's mask is so good that he spends most of the second season as a Hidden Villain. In "The Zinit", he finally ditches the mask and reveals his true self: an Ax-Crazy, nihilistic Omnicidal Maniac who is even less mature than Yugo despite being far older.

Real Life

• The psychology text The Mask of Sanity offers several insights on this point. Genuine psychopaths aren't like the Hollywood trope of a psychopath. Rather, they seem utterly incapable of empathizing with other human beings. Subsequent psychology research on imprisoned psychopaths with neuroelectric instruments has actually measured that their brains seem structurally deficient in the areas responsible for emotion. In normal people, when shown violent or offensive words such as "murder", "rape", etc., neural activity spikes in the parts of the brain responsible for emotion, i.e. the amygdala. In psychopaths, there is no similar activity spike: their amygdalas seem stunted and dead. The great unanswered question is the Nature Versus Nurture debate: whether they were born with non-functioning amygdalas, or if years of systemic childhood abuse stunted their mental development. The end result is that psychopaths have all of their higher brain functions intact such as speech, reading, and higher logic — but human emotions are an alien sensation to them. They have the raw intellect of an adult, but their level of emotional understanding and empathy for others is comparable to that of a selfish toddler, who does not yet understand that other people's lives don't revolve around them.
  
  The argument made in The Mask of Sanity is that because psychopaths still have their raw intelligence, they can through careful analysis over the course of their lives gradually learn to very accurately mimic the normal emotional responses that other people expect of them: if they cut ahead of someone in line, they understand that they're supposed to say the words "I'm sorry", but the words have no meaning to them. They learned it as a rote response— but as the book points out, mimicry, no matter how careful, is still not comprehension. So sort of like a human Chat Bot, psychopaths have learned a lot of stock phrases for "small talk", but it's just by rote: chit-chat about the weather, complimenting someone on losing weight, etc. This can also make them come off as very obsequious, when they're trying too hard to convincingly act like a caring, normal person. The book advises that, to discover a psychopath, all you really need to do is engage them beyond surface-level conversation for any length of time, i.e ten minutes of talking about "What are your views on violent crime?" and they'll eventually say something bizarre, revealing that they're just attempting to appear normal as best they can grasp it. It's very much like the Voight-Kampf test from Blade Runner: ask them emotionally provocative questions, and they won't know how to properly respond as a normal person would.
  • For example, consider the case of infamous convicted child molester Jerry Sandusky. When asked short yes or no questions, he could keep up the act, such as "did you molest boys when you were a coach?" ("No") — but any interview of length that he gave, he would start rambling off on bizarre and incriminating tangents. Particularly the bizarre telephone interview on live TV when asked the more involved question, "Are you sexually attracted to young boys?", instead of immediately and flatly saying "No", he started pondering the question aloud because he wasn't sure how a "normal" person would respond to such a question, leaving the interviewer to roll his eyes at his absurdity.
  • Serial killer John Wayne Gacy is often pointed to as a prime example of a psychopath who was able to put on the façade of a seemingly "normal" domestic life, but it was all just an act. He seemed to have a normal house in the suburbs (despite his rocky marriages), but he was storing dozens of bodies of men that he had killed in his crawlspace.
  • High-functioning, when used in the context of mental illness, refers to someone who's able to do this, and consequently they're generally harder to spot and might not get the treatment that they need.
  • The concept of neuro-plasticity complicates this trope further. Essentially, it is now known that one can actually change the way that one's brain works through experience, beliefs, or other habits or methods, deliberate or otherwise (though probably only around 50% of our brain at most is capable of this, and it becomes harder as we age as our brain settles into patterns— barring brain damage, that is). In other words, it is possible that normal people can become psychopaths (or at least psychopathic) through committing terrible deeds, or perhaps even just researching or dwelling on them long enough to lose their natural aversion or disgust to them, and perhaps even the memories of that disgust. Conversely, of course, this means that just because someone becomes desensitized to acts or conceptions of violence or other behavior doesn't mean that they are actually likely to commit it, nor that they are incapable of emotions or empathy, so it may be harder to tell apart genuine functioning psychopaths from ordinary people who are just "used to it", as it were.

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