Ambiguous Disorder

This character's behaviour is so bizarre, so clearly outside the norm, that Real Life psychologists would be scrambling for the diagnostic manual to try to figure out what to diagnose them with. It's way beyond mere ordinary quirkiness. No reasons are given for the strange behaviour. No specific diagnosis is ever mentioned in the story. In fact, any resemblance to any real disorder is likely accidental; the character's symptoms are exactly those symptoms the writer wants them to have. It is a case of Ambiguous Disorder.

The disordered behaviour will almost always be Played for Laughs. This technique is generally used to avoid writing yet another Patient of the Week about some specific disorder and to focus in on the comedic elements without having to deal with the serious issues associated with real disorders.

Compare Soap Opera Disease and G-Rated Mental Illness.

Anime and Manga

 * Osaka from Azumanga Daioh thinks in ways so completely different from other people that it's easy to think she might be mentally disabled. She's dreamy and inattentive, prone to weird misunderstandings, has very poor motor control, and occasionally seems to suffer from actual hallucinations. But although she seems mentally slow, she gets only slightly below average grades at a regular school and manages to socialize more-or-less normally. She even has some Genius Ditz tendencies: she's prone to penetrating insights that escape all the other characters, she's surprisingly well-versed in some obscure topics like marine biology, and her odd way of looking at the world makes her extremely good at certain kinds of riddles.
 * The joke here — which can easily escape Western viewers — is that Osaka's spacey, laid-back personality makes her a humorous inversion of the stereotypical brash, loudmouthed, Hot-Blooded Idiot From Osaka.
 * Apachai Hopachai of Kenichi: The Mightiest Disciple acts childlike to a degree that goes way beyond the usual Man Child level.
 * Inspector Lunge from Monster. Absent staring, hand-tics, Spock Speak, socially clumsy, isolated, compulsively obsessive. It's especially weird that nobody ever mentions any possible diagnosis, considering the manga's protagonist is a doctor and several characters who are psychologists, though mostly of the forensic variety, also feature prominently.
 * Death Note:
 * L, the master detective and profiler. Despite his incredible analytical skills and the social finesse he shows in interacting with his nemesis Light, he's extremely eccentric and seems to have serious trouble intuitively grasping normal social interplay. Prominent entries on his long list of quirks include weird and awkward body language, total obliviousness to the idea that blue jeans and a pajama top might not be appropriate attire for every possible situation, and a really extreme sweet tooth.
 * L's successor Near is very similar, maybe even more so.
 * Bakuman｡: Eiji Niizuma has extremely odd sitting patterns, demonstrates some trouble with social conventions and nonverbal clues, and has an obsessive interest and talent in a particular subject.
 * Ice Queen Aiko Iwase also qualifies.
 * Edward from Cowboy Bebop is ludicrously intelligent, but shows absolutely no ability (or inclination) to socialize in a remotely normal fashion for even brief periods. She almost always skips, cartwheels or dances instead of walking, and she sings improvised songs about whatever she's doing, often as a substitute for normal conversation. Her closest friend is a hyperintelligent, non-talking dog.
 * In Umineko no Naku Koro ni, Maria has bizarre reactions (or a notable lack of the same) to events around her, and she never seems to be able to avoid hitting her mother's Berserk Button when she really should know better.
 * White from Tekkon Kinkreet: there's definitely something mentally different about him, but it's impossible to distinctly tell what. He's exceedingly childish for his age, refusing to bathe unless prompted, and is unable to tie his own shoes at age ten. Yet at the same time White has a... vivid imagination and occasionally a strange, almost cosmic insight.
 * Detective Conan:
 * Hattori Heiji's really thick about other people's feelings, bad at picking up social cues, and extremely awkward a lot of the time. He can't lie without stuttering and giggling like an idiot, and he latches onto ideas or interests and does not let them go. For example, when he first became friends with Conan, he talked about Shinichi SO incessantly that his childhood friend believes him to have a girlfriend in Tokyo with the last name Kudo. He's also extremely adept at remembering little details and noticing anything out of the ordinary, no matter how minor.
 * The protagonist, Shinichi Kudo/Conan: In the first episode, he does not know when to stop rambling on about Holmes and Conan Doyle, and talks to Ran about it the entire time they are at the roller coaster. Even whenever he dates her and starts off wanting to tell her his feelings, instead he ends up gabbing about Holmes again. He is not very social, and it is implied that many of his teachers and classmates believed him to be arrogant and self-absorbed. Also, he seems to be quite blunt and unaware of social tact.
 * Considering how quirky most of the characters in Eyeshield 21 are, the fact that both Shin and Tetsuma are both considered a little "off" by both the other characters and standards of the series says something:
 * Shin speaks in monotone with textbook level formality, has an encyclopedic knowledge of everything related to physical fitness (he maintains a VERY strict nutrition plan and seems to be very well-read on human anatomy), and absolute devotion to improving himself as a football player. At the same time, he speaks his mind in the most direct way possible (both positively and negatively), has no interpersonal skills or awareness of social norms (he doesn't see anything wrong with walking around shirtless), and is completely oblivious about anything that's not football or school related (when his teammate Sakuraba grows a beard, gets a crew-cut, and starts training harder, the only thing Shin notices is that Sakuraba's muscle tone has improved). Nonetheless, he's very respectful and always means well, so the few friends he has seem to take his many idiosyncrasies in stride.
 * Tetsuma is very literal-minded, even more oblivious to social norms then Shin (as well as being an expert on his position), and can't seem to function normally without his best friend to tell him what to do. When he does speak (which he'll only do if someone specifically tells him to speak), it's very robotic and formal. Most likely because of his difficulty in interacting with people, he dearly treasures his friendship with Kid, who accepts him regardless.
 * Lain in her initial appearances within Serial Experiments Lain; she shows impairment in the use of nonverbal behaviors, has developed few peer relationships, and the ties with two of her friends are very weak. She does not show enthusiasm to seek enjoyment or socialization with others, and lacks social or emotional reciprocity. She also rarely speaks, and cannot converse well or start/hold a prolonged conversation. Finally, she becomes unusually enthralled by computer/technological objects and their construction as the series goes on. Never mind the loss of sense of time and space, vivid hallucinations(?), moments of amnesia, hearing voices...
 * Jirarudan/Lawrence III from Pokémon 2000: He's an art collector of a ridiculously high magnitude who seems to have learned social skills entirely by rote; has a narrow and fixed attention span; wears a long coat with an undershirt to tropical islands in the middle of summer; has almost no change in facial expression or vocal intonation despite living by his passions; seems to have difficulty recognizing cues from others; and takes everything, including the legend and Misty screaming at him, only by the words presented without considering tone or alternate meaning.
 * Almost every mage in the Nasuverse who isn't a Complete Monster could qualify for this at some level. They're socially distant, obsessed with their own singular interests (their magic fields, their Origins and the Akashic Records in this case), and frequently have special repeated tics or actions associated with activating magecraft.
 * Nozomu "Mr. Despair" Itoshiki of Sayonara, Zetsubou-sensei. Focuses on one topic for an incredible amount of time; depressive and paranoid to a nearly delusional degree (although it's Played for Laughs); and is a self-proclaimed master of not looking people in the eye.
 * Yuuki Rieko of 14Juicy displays a limited emotional range and seems to have no interest in, or aptitude for, anything but soccer.
 * Sawako from Kimi ni Todoke. At the age of fifteen she's never made a single friend, and frequently misinterprets social cues with hilarious results. She doesn't seem to find this at all weird.
 * Durarara!!'s Shizuo Heiwajima is such a textbook case of intermittent explosive disorder (albeit a very exaggerated example) that one has to wonder if Narita had the DSM-IV in hand while he was thinking up his character. His brother Kasuka also qualifies for this trope.
 * Amuro Ray of the original Mobile Suit Gundam is capable of social interaction, but absolutely hates it. He's paranoid, prone to focusing on himself, and in his Establishing Character Moment, is shown sitting in his room in his underwear, not having eaten in a day, and looking at a computer chip through a microscope while studiously ignoring the evacuation siren blaring outside. His friend Frau specifically states that this isn't uncommon behaviour, and that his neighbour was supposed to come in and tell him if the siren was going off. Needless to say, there are some debates in the fandom as to just what, if anything, he might have.
 * Kira Yamato of Gundam Seed shares many of Amuro's personality traits; the main difference is that he tries to be social (despite sucking at it) while Amuro deliberately avoids other people at all times.
 * Zeta Gundam's Kamille Biden is what you get when you take a very Amuro-esque personality (love of machinery, poor social skills, mild paranoia) and combine it with some serious daddy issues. Big Bad Paptimus Scirocco shares many of these personality traits, and compensates for them with his Psychic Powers.
 * Shu Ouma from Guilty Crown is an Extreme Doormat with No Social Skills who admits to himself that his mind might be out of step with everyone else's, and has only made "friends" by going along with what other people say. When he makes a carelessly cold remark about someone else and is reprimanded for it, he can only think about his own feelings that were hurt, rather than feeling bad about what he said. He also has trouble with making eye contact with other people.
 * Komi Can't Communicate; the disorder that keeps Komi from speaking or interacting with others is never given an official name.

Comic Books

 * Marv from Sin City is often considered stupid and insane, an opinion that he shares. He did poorly in school, has No Social Skills, gets "confused" a lot, and often has violent blackouts. In his first story, he mentions that he has always been good at puzzles, implying that he's capable of solving complex mysteries. He was certainly intelligent enough to go up against a powerful crime family. He also cares a lot about his friends and family, is friendly towards complete strangers, and is something of an awkward gentleman with women. On the other hand, he often displays bizarre emotional responses, most prominently a near-sociopathic Lack of Empathy—there have been multiple instances of him remaining genuinely perfectly calm during moments of intense chaotic violence, and he's capable of cool, calculated cruelty and a complete lack of queasiness or discomfort while casually torturing people to death.
 * At the beginning of The Stupiders we are told that everyone has at least one problem or quirk, but what exactly those problems are is left up to the reader to discern.
 * Every Batman villain, as well as Batman himself in some interpretations.
 * Brian of Knights of the Dinner Table. He has a job that involves running an online service from his home (which he is said to not clean) and painting model figurines. He has a savant-like memory of obscure roleplaying game rules, yet sometimes forgets his own phone number. He is stated to become very uncomfortable when any social group exceeds four to six people, especially when it happens away from the context of a shared interest. He rarely speaks unless dealing with gaming, and has a face and body language that is usually unreadable. And finally, some things that would annoy other people seem to have no effect on him at all, while something that others would take in stride can send him into a sudden and brutal fury, typically involving flipping over the gaming table in rage.

Film

 * The Wizard: Jimmy, by way of The Rainman with the way he plays video games.
 * The Social Network: Zuckerberg. He cannot hold down a single topic in a conversation. He shows very little tact as well, as an offhand comment he makes to his girlfriend causes her to break up with him. In short, he is much more at home with his computers and code than he is with other human beings.
 * Sherlock Holmes: Robert Downey Jr.'s portrayal in the 2009 film and its 2011 sequel was more socially challenged than usual, had some weird eye contact moments, and was implied to have issues with sensory integration.
 * Martian Child: The titular character is a young boy who doesn't understand facial expressions (he takes pictures of other people's facial expressions to try and puzzle them out at his leisure) and has multiple sensory issues (he wears a weight belt all the time to keep from "floating away", is overly fond of seat belts, and can't stand sunlight).
 * Denny in The Room seems completely ignorant of social norms and generally acts much younger than his apparent age, at one point leaping into bed with Johnny and Lisa as they are about to have sex. In an interview, director Tommy Wiseau admitted that Denny is "retarded, a little bit," but he failed to tell the actor that or spell it out in the script, so the performance is confused.
 * Napoleon Dynamite: Napoleon, Kip, Pedro and Deb all display really, really severe social awkwardness and fixations on various unusual subjects (e.g. ligers).
 * Seance: A character is antisocial and awkward, and takes an unnamed medication that he claims is supposed to make him "normal".
 * Garth from Wayne's World. His speech is stilted, he doesn't eat anything that isn't brightly coloured and fruity (to the point of eating a jelly donut with a straw), goes off on some extremely bizarre tangents in conversations, and spends hours obsessing over strange mechanical gadgets.
 * Freddy Got Fingered: Gord is a gigantic Psychopathic Manchild who is a social reject to say the least, is somehow insane enough to still live with his incredibly abusive father, is Literal-Minded enough to interpret someone telling him that becoming a respectable Funny Animal animator requires him to be able to "get inside the animals" as a suggestion for him to cut a road-killed deer's stomach open and then wear said deer's corpse on top of himself, and even cuts women's umbilical cords by biting them in half with his teeth.
 * Lilo in Lilo & Stitch has a bad case of All of the Other Reindeer, but unlike many examples of that trope, she really is a genuinely strange little person who weirds out her "friends" with a strange mix of eccentricities, behavioral issues, social inappropriateness, and unusual interests (not many six-year-old girls these days are obsessed with Elvis).

Literature

 * Ignatius J. Reilly from A Confederacy of Dunces. He's a hoarder, a massive conspiracy theorist, and an extreme luddite and creature of habit.
 * Lisbeth Salander of The Millennium Trilogy. She exhibits several oddities, including Photographic Memory, extremely selective interests (mathematics and computer hacking), and very few changes in expression or vocal tone. The author said he envisioned her as somebody who has turned into "somewhat of a sociopath" from incredibly traumatic experiences, or how a modern-day Pippi Longstocking might turn out after growing up as an mentally odd orphan handled by the somewhat infamous Swedish bureaucratic system.
 * In the book Changeling by Delia Sherman, it's strongly implied that Changeling has been diagnosed with something, but it's never stated what.
 * Colin from An Abundance of Katherines—his social skills are a mess. His only real friend in high school actually needs to tell him when his conversation topics are boring. They become friends after he thinks it is funny to refer to his eye as a "pupillary sphincter." His friend, who was home-schooled up until that point, remarks something along the lines of, "I've only been in public school for 2 days, and I know that your sphincter is not something you talk about."
 * In Peter F. Hamilton's The Dreaming Void, implants giving people their own built-in "heads-up display" are ubiquitous, but only Troblum is described as having or needing a "protocol behaviour program" to prompt him through ordinary social situations. He's got an obsessive interest in a thousand-years-past war (that just so happens to be the subject of the two previous books set in that universe) and is explicitly stated to have no real ties to anyone in the Commonwealth.
 * Sherlock Holmes as portrayed by Sir Arthur Conan Doyle. Later depictions of the character can differ, but the original stories make it fairly clear that it's not just that Holmes is incredibly smart—his brain works in a different way from most people. He's got a hefty dose of social awkwardness and assorted weird behavioral quirks to go along with the extreme intelligence and perspicacity, as well.
 * The Curious Incident of the Dog in the Night-Time: the main character is clearly non-neurotypical, and readers almost invariably assume he's autistic, but no diagnosis is stated in the book—and in fact the author has said he didn't intentionally base the character's behaviour on any specific disorder.
 * Daymar the wizard from the Dragaera books is truly brilliant, but also extremely Literal-Minded, and oblivious to social cues unless they're explicitly spelled out—and after they are explicitly spelled out, he never shows even a trace of embarrassment about how awkward his own behavior was.
 * Charlie in The Perks of Being a Wallflower is a more serious example of this. He was held back for being "emotionally damaged", but the disorder is never named. He seems to have trouble in social situations and seems to be very sheltered from normal life.
 * Bella from Twilight. By her own admission, she has trouble connecting with people in general. Apparently her only friend in Phoenix was her mother, who she still forgets to write to when in Forks. She becomes extremely obsessed with things like becoming a vampire, while making no plans for things like college or a career. She becomes so unhealthily obsessed with Edward that when he leaves her, she first is catatonic and then makes no effort to move on with her life, instead choosing to spend her college money on motorcycles and nearly killing herself cliff diving. She gives very little thought to the consequences of her actions, and tends to not understand why people react the way they do. A lot of her traits (her lack of desire to have an adult life, her general Lack of Empathy, her repeated lack of regard for her father's house rules, etc) hit all of Dr. Hare's checklist points for sociopathy.
 * The narrator of Oh, the Humanity!: A Gentle Guide to Social Interaction for the Feeble Young Introvert has a pretty spectacular one, mixed with generous doses of denial and Know-Nothing Know-It-All. Traits include an obsession with germs, total disinterest in other people's lives ("I meant to call you to tell you you have so much to live for...I'm sorry, I've just been doing so much gardening lately"), a grasp on human interaction that can at best be called fumble-fingered, an inability to focus or prioritise (at one point delaying a pub crawl for two hours because he forgot to give his parakeet its ear medication, and didn't like to wake it up), and massive, hubristic pride in the social skills he does not in fact possess. It's unclear how much of this emerged from his Hilariously Abusive Childhood.
 * A side story in The Dresden Files, told from Murphy's point of view, makes Harry Dresden an in-universe example of this: From most Muggles' viewpoint, Dresden, a self-declared wizard, has a tendency to poke around crime scenes, looking or asking for things like toenail clippings or hair straws, mumbling to himself and never looking people in the eyes. In addition to this is his at time dubious personal hygiene, Man Child personality, near-pathological need to snark at and gainsay authority figures, and Nerves of Steel that makes it unnerving when he seldom shows outwards reactions to things normal people would lose their wits over. The end result is that it makes him seem, at best, a high-functioning but very eccentric autistic. By reading most of the books (which are from Harry's point of view), most of these behaviour patterns are explained logically, but that doesn't make him seem any less weird to the muggles he must uphold The Masquerade to.
 * Gracie Milne, a minor character in Tipping the Velvet, is a bit like this. She doesn't really have any identifiable symptoms, but she's definitely more than a little odd, acts rather young for her age, and she may have sensory processing differences considering her fixation with colors.

Live-Action TV

 * Coronation Street: has Roy Cropper who is simply seen as odd by his neighbours with his bizarre lectures on really trivial subjects, fascination with details, and that little bag he carries everywhere.
 * CSI: Gil Grissom. His level of social understanding fluctuates between episodes, along with his attention to trivial details and love of bugs.
 * Law and Order: Criminal Intent: Detective Robert Goren; it's suggested he simply never learned proper social skills growing up because his entire family suffered from one mental illness or another. Goren is what happens when the genetic dice are loaded to roll Snake-Eyes and come up Lucky 7 anyway.
 * The Big Bang Theory:
 * Sheldon is socially challenged, has fairly monotonous speech, and exhibits heavily ritualized behavior. He even has hypersensitive hearing; the others refer to it as "Vulcan hearing" and are usually cursing it due to his overhearing things they wish he didn't.
 * Another example is Sheldon's Distaff Counterpart Amy Farrah Fowler.
 * Abed from Community. He is incredibly fascinated with films and television and is a bit obsessed with projecting their tropes onto real life. He also has a strange, somewhat sterile demeanor, doesn't seem to know (or even when corrected, care about) how to go about certain social situations, and is face-blind.
 * Lampshaded in Advanced Dungeons and Dragons when he is referred to as "Abed The Undiagnosable".
 * In one deleted scene, a drunk Abed was speaking only in a neverending string of self-describing movie quotes, but randomly grunted "high-functioning" in the middle of his rant.
 * One of his lines in the Regional Holiday Music Christmas rap song Jehovah's Secret Witness is "On the spectrum? None of your business."
 * Abed's "mental issues" have been present since his introductory scene in the pilot, where he rattles off everything he knows about Britta from their one conversation including that she has a brother who "works with children with a disorder I might want to look up".
 * Matthew Gray Gubler claims that he plays Spencer Reid from Criminal Minds as autistic, something that's never been confirmed. The only time that the possibility did get a mention in the show is when a villain described Reid as having autistic leanings, but this was part of an extremely inaccurate Hannibal Lecture delivered to this entire team. (Reid's issues may, however, stem more from his difficult childhood and equally difficult job.)
 * Spinelli on General Hospital. Nicknames everyone, Sesquipedalian Loquaciousness...but when Dr. Matt Hunter suggests undergoing tests for autism, he refuses, saying "I am me".
 * Reginald Barclay from Star Trek: The Next Generation shows severe social anxiety, along with an obsessive streak and a compulsive tendency to retreat into fantasy.
 * Buffy the Vampire Slayer: Anya—at first viewers are led to believe her complete lack of social skills is a result of having been a demon for centuries, but eventually it's revealed that she acted exactly the same before she became a demon. The flashback showing this is extremely silly, however—one might chalk it up to Rule of Funny.
 * Michael Scott of The Office -- No Social Skills, near-total inability to understand metaphors, sarcasm or hyperbole, savant-like skills in regards to sales, very strong indications that he has never had any friends, and overall behavior that no normal person would believe was acceptable. This pops up in a lot Steve Carell roles.
 * Cal Lightman of Lie to Me. Quite socially uncomfortable, with a very fixated interest on lies and facial expressions as well as psychology. He destroyed his own marriage because he couldn't switch off.
 * Dr. Walter Bishop of Fringe started like this,.
 * All indications are he was already an eccentric genius before the elective brain surgery, though.
 * Alternate Astrid is highly intelligent, gravitates toward Spock Speak but makes realistic exceptions to it, and doesn't look at anyone when she talks. In her A Day in the Limelight episode, we learn that she is fully aware that she isn't "normal" and feels incredibly sad and frustrated that she couldn't relate to her father the way she wanted to.
 * Bernard Black of Black Books. Very socially awkward and uncomfortable with changes in an extremely repetitive routine.
 * NCIS: Lab Rat Abby Sciuto. She is very good at what she does and shows a childlike sense of joy while working, she will often give long-winded and highly technical speeches when explaining something, she is extremely attached to and protective of those she cares about, and she becomes almost unable to function both professionally and personally if she has to dress in anything other than her typical goth style or can't listen to her music while working.
 * Chloe O'Brien of Twenty Four. It's not mentioned as any sort of possible mental illness in the show; other characters just vaguely refer to her as having an odd personality. She is often blunt to the point of rudeness, easily irritated, especially when she is in the middle of something, and is generally dismissive of other people. She is, however, not without empathy. She usually isn't aware she's engaging in behavior most would find odd or annoying until she notices the way people are looking at her. It's just that most of the time, she doesn't care.
 * RO from Sea Patrol has a very black and white view of the world, and when asked if this was true he responded "I'm not racist." Then there's his believing Bomber fancied him after she gave him a peck on the cheek, and him not wanting to take credit for saving her life because she told him not to go near her.
 * Renfield Turnbull from Due South is just odd, even compared with Bunny Ears Mountie extraordinaire Benton Fraser. Some fans have wondered how someone with his apparent emotional volatility and clumsiness ever made it into law enforcement.
 * In Bones, both Temperance Brennan and Zach Addy display a lot of problems with social skills and other issues.
 * In Raw Philip displays poor social skills, is incredibly awkward at making small talk, likes to keep orderly lists and cooking is his big obsession.
 * Leon from Tucker is obsessed with Mexican wrestling and sea creatures (even sponsoring an octopus) and has a strange collection of human hair.
 * Brick Heck on The Middle. He has the Verbal Tic of, at least once each episode, repeating what he just said in a whisper while looking downward. He's in a special social skills class at his school. He is obsessive about reading almost continually, to the point that he's delighted to get a toy robot for his birthday ... because the instructions are in different languages, and he hopes to learn Japanese that way.
 * Saga Norén of The Bridge has No Social Skills to an extreme degree, is shockingly lacking in apparent empathy and compassion, and has an extremely rule-bound attitude to life. The actor and creators have said that she probably is somewhere on the autistic spectrum, but that they deliberately didn't state it explicitly or work from a list of recognised symptoms because they wanted to write her as they wished without misleading or offending people.
 * Sherlock, much like the source character, is obsessively detail-oriented, generally displays a lack of affect, needs to be mentally stimulated at all times, seems to have very little regard for or understanding of others' emotions (but can manipulate them very capably when he really wants to), and tends to be astonishingly self-centred. People who dislike him describe him as "a psychopath," his best friend half-jokingly refers to his "autism," and Sherlock describes himself as "a high-functioning sociopath." All these diagnoses seem to come pretty close, but none of them quite entirely fits.
 * Lucy Payne in DCI Banks, apparent in the first sequel. A strange combination of post-traumatic stress disorder, masochism, an apparent lack of social skills rendering her a loner, while at the same time being a surprisingly good manipulator, and highly suggestible herself. Plus she's apparently quite indifferent to other people's suffering. Her emotional state wavers between Tin Man and bouts of anxiety. And all that combined with a somewhat stiff mimic and posture, and a prosody that is either exaggerated or nonexistent. At first it appears like she's simply the victim of her husband's domestic abuse; however, it later turns out . While some members of Banks' team assume she must be psychotic, he himself insists she has - and has always had - sound judgement. The fact that, and her Villainous BSOD at the end of the sequel don't make it any easier to judge her mental state. Psychopath? Insane? Or an unfortunate combination of Asperger Syndrome with a highly abusive past? Or dependent personality disorder turned Up To Eleven? An extreme case of Stockholm Syndrome? All of that comes close, but doesn't fit really well. (The fact that she has just probably plays into this as well.)
 * To a lesser extent, DI Helen Morton fits this trope as well, being The Spock of the team, especially in her early appearances. And in a later sequel, she's the only one out of the team who really understands an autistic teenager.

Newspaper Comics

 * Calvin from Calvin and Hobbes: Highly intelligent for his age but performs poorly in school, prefers associating with his (possibly) Imaginary Friend to socializing with real people, tends to retreat into an unusually rich fantasy life, has many strange Cloudcuckoolander quirks, can be a stickler for his own personal schedules and standards of behavior, and doesn't understand why people act the way they do.

Video Games

 * Oracle of Tao: Ambrosia has a Sugar and Ice Personality, coupled with dramatic Tsundere moments, and occasionally has rather dramatic depressive episodes. You'd probably say she's bipolar, except her down periods are more flat, like a schizoid. She also has serious fears that she doesn't exist, and that she's hallucinating the entire game events. Add a few Axe Crazy episodes, and you get a very strange picture.
 * The Tales (series) has quite a few examples.
 * Tales of Symphonia has Raine Sage: a cold and calculating, but incredibly intelligent young woman who normally acts like an aloof mentor who always has to be right... and who devolves into a child-like state the moment she discovers a temple ruin, an ancient weapon or anything to do with the civilisations of past eras. She's also shown to have difficulty relating to the other party members, especially in the anime where her Ice Queen elements are really played up. It's mostly treated as comedic, as her similarly-bright sibling Genis is just plain embarrassed by her enthusiasm (at one point, she even descends into maniacal laughter over the insides of an old temple).
 * In a sidequest, you can learn that her mother also fits the bill. It's not clear what's the matter with her
 * In Tales of the Abyss, most of the characters show some kind of dysfunction, but only one of them has the dysfunction as the cause of their backstory, instead of the result: Jade Curtiss. He's bizarre when you first meet him - highly intelligent and mixing traits of Stepford Smiler and Stepford Snarker into one darkly humorous mask of unreadability. You later learn that as a child, he never showed any outward emotion besides a confidence in his skill and intelligence that extended into arrogance, that he liked to kill even weak and harmless monsters, and that he's 'never understood what it means to die'. He also shows some social awkwardness (in one skit, he joins Anise in tickling Guy as if he either doesn't understand or doesn't care that what's cute from a fourteen year old girl is weird from a thirty-five year old man) and obliviousness to his own emotions (in the Disc One Final Dungeon, Anise points out to him that he must like and respect the other party members, and Jade seems genuinely surprised to realize that she's right).
 * From the same game, Guy Cecil freaks out every time a woman makes physical contact with him.
 * Pascal in Tales of Graces seems to have rather strange obsessions and does not understand exactly how socially awkward she can be at times. Her immature behavior makes many players surprised to discover she's 22 years old (although the visual design for her character doesn't help).
 * Heavy Rain has Norman Jayden. He's shown to be socially awkward and has difficulty carrying on normal conversations,
 * Otacon from Metal Gear Solid—socially awkward, rather Literal-Minded, obsessive, tends to retreat into fantasy, extremely emotional. This may all be explained by his traumatic childhood (which involved ), however.
 * There's explicitly something wrong with the title character of American McGee's Alice, but the PTSD from her family's deaths doesn't explain the hallucinations, delusions, or episodes of mania and catatonia so severe she was institutionalized. When asked later on, American McGee confirmed that this game was a "natural extension" of the Alice series going under the assumption that the previous stories weren't either fantasies or real events, but hallucinations she honestly thought were real.
 * Although Yamaku Academy supposedly caters only to students with physical disabilities, Katawa Shoujo still has several examples:
 * Kenji is obsessed with delusional conspiracy theories to a degree that would probably have psychologists scrutinizing him for schizophrenic tendencies in Real Life, although unlike all the other disabilities in the game this is purely Played for Laughs.
 * Rin's behavior is just plain weird in a way that's hard to pin down: she definitely does not think like most people, and her behavior and comments can be socially inappropriate, not in the manner of someone who doesn't understand normal social interaction but more as if she simply doesn't care. In any case, having no arms may not be her biggest problem.
 * Misha is an inverted variant. She has no obvious disabilities, so many players are left wondering why exactly she's at Yamaku. She's a bit quirky (energetic, laughs a lot, has some volume control issues), but not to the point that she'd be considered seriously mentally unstable, and Yamaku is not supposed to cater to mental disabilities in any case. Certain scenes imply that she came to Yamaku for other reasons: namely, she wants to be a sign language instructor and Yamaku is one of the only schools that has sign language courses.
 * Dutch van der Linde from the Red Dead Redemption series reads almost like a textbook example of Borderline Personality Disorder. He has grand delusions of outwitting the US government, is prone to irrational decisions and violent emotional outbursts, obsessively distrusts many members of his gang to the point of paranoia, and has a tendency to snap between loving his surrogate sons and despising them as ungrateful "traitors" with absolutely no middle ground. His startling Lack of Empathy towards the people he hurts and inflated ego combined with many of these traits also hint that there's a bit of Narcissistic Personality Disorder thrown into the mix. And thanks to a lot of these issues getting worse in the wake of a head injury during a heist gone wrong, he might also be suffering from brain damage of some kind.

Western Animation

 * Steve Smith from American Dad. Several episodes prove that he's capable of extreme violence, self-abuse, and just plain undiagnosable problems for laughs. Roger even lampshades this with his response to Steve's plan to exact revenge on a bully by dressing up like a girl and seducing him: "Yes, let's keep that plan between you, me, and the string of therapists who won't be able to help you."
 * Cleveland, Jr. from The Cleveland Show. He's a teenager with the mentality of a child, and has a number of disturbing quirks, such as an obsession with cleanliness and order, and random bursts of violence (such as strangling a mannequin head for being "so pretty"). He also believes one of his stuffed animals is alive, to the point of hiring a nanny for it.
 * It seems to be hinted that Ed from Ed, Edd 'n' Eddy has some kind of a disability.
 * My Little Pony:
 * Draggle from the original shows signs of many disorders, and by default of her family life, Stockholm Syndrome. Also, her voice in "The End of Flutter Valley" indicates, erm, slowness due to Flanderization messing with her intelligence.
 * In the 2010 series, My Little Pony: Friendship Is Magic, Pinkie Pie is a really eccentric Cloudcuckoolander who seems to inhabit normal reality only part-time and is almost pathologically cheerful and silly...except that when a wacky misunderstanding makes her believe her friends are excluding her, she immediately snaps into a state of paranoia and psychotic depression so severe that she becomes delusional and starts hallucinating. (This is vaguely hinted to have something to do with her rather dull and depressing childhood, but we don't know if the story about her childhood was true and in any case that doesn't really seem to be enough to explain it.).
 * With Cheese from Foster's Home for Imaginary Friends, you can't really pin down what's wrong with him. He clearly was imagined by a special needs child (this is made painfully obvious when he's introduced), but what exactly that special need was is left ambiguous. Most likely it's just an amalgam of general "mentally challenged".
 * King of the Hill: Dale is an awkward, paranoid Cloudcuckoolander whose conspiracy theories border on outright delusional—and yet despite his constant suspicion of everyone and everything, he's completely oblivious to actual conspiracies that are obvious to absolutely everyone else, such as his wife's affair with John Redcorn.
 * Worse than Dale is recurring antagonist Jimmy Wichard. Something's wrong with him that makes him aggressive, stupid, antisocial, and unstable, but it's not clear what. Dale claims this happened as a result of staring at the sun too long, but then also adds, "He couldn't have been too smart to do something like that in the first place. Kind of a chicken and egg thing."
 * Baljeet of Phineas and Ferb. Extremely dependent on routines and clear direction, socially introverted, observant but somewhat oblivious and emotionally stunted, able to focus for long periods on repetitive behaviors.
 * Invoked with the "Newton" disguise of Octus from Sym-Bionic Titan.
 * Ed the otter from Brandy and Mr. Whiskers has something. He has awkward speech patterns, uses big words, he's also a bit on the stoic side for the most part and is also physically clumsy when it comes to sports.
 * Nonny from Bubble Guppies is a smaller example. He rarely ever smiles, has a bored, monotone voice, and is quite awkward compared to the other guppies.
 * Daffy Duck in The Looney Tunes Show (carried over somewhat from older cartoons in which he was clearly insane, but not debilitatingly so). Bugs Bunny guesses that he's "a sociopath, "a Narcissist" and "probably a psychopath". (He also sometimes seems to be unable to tell fantasy apart from reality—just see the music video for "The Wizard.")
 * Ralph Wiggum from The Simpsons. He acts much younger than his age, has weird mood swings, is quite the Cloudcuckoolander, doesn't seem able to tell fantasy apart from reality, and it's implied that he hears voices. He's also implied to be on meds.
 * It is revealed in "Moms I'd Like to Forget"
 * Clarence's grandmother Dilliss appears to have Obsessive–compulsive disorder (OCD) and Dementia. This has been shown in "Hurricane Dilliss" when she: judges Mary's new boyfriend Chad, possesses dozens of items, disrupting everyone's sleep while trying to help Clarence with his school project, rudely enters the bathroom while her daughter is using the shower, and makes the house a huge mess at night.