The Mentally Disturbed

Except for extreme cases such as paranoid schizophrenia, or conditions with sympathetic social connotations (Down syndrome; severe autism), there is a tendency in media to regard mental disorders as some kind of put-on or character flaw, that is at best amusing, at worst annoying (not that the extreme illness are exactly treated like cancer-victims-- in fact they can be treated worse than milder forms). The two most "comical" conditions are Obsessive-Compulsive Disorder and Tourette's Syndrome, both of which can be significant, sometimes disabling problems in real life.

At the very worst, a person is portrayed as being completely able to break out of their illness if they were to simply try hard enough-- i.e. they're just plain lazy in addition to the behavior itself. Depressive? Cheer up (and stop being lazy)! Manic? Just take a deep breath and calm down. Obsessive-compulsive? Relax already. Delusional? Get a grip on that overactive imagination. An eating disorder? Please. You look fine! Hyperactive? Control yourself, my God. Paranoid? It's not all about you, you know! Anxiety with panic disorder? Suck it up, coward! Severe trauma from abuse during infancy? Grow up and over it!

A very nice character will, however, treat the mentally disturbed with kindness and will nicely ask whether they went off their meds and that's why they're acting up again.

This prejudice contributes to the mentally disturbed being Acceptable Targets for the most merciless cruel humor and parodization; this pertains to sociological stereotypes that most people will tend to blame the victims of misfortunes, in order to take credit for their own good fortune, rather than owning it up to plain luck of the draw (often because luck runs out, and this means that it's only a matter of time for them).

Note that this also pertains to the illusion of control that society presents regarding one's mental state, vs. one's physical state; i.e. few, if any, will blame victims of cancer (except for lung cancer), leukemia, or similar organic physical illnesses or injuries, telling the person to "toughen up and get over it," or otherwise calling them "weak" or "lazy."

See also: Insane Equals Violent, Funny Schizophrenia, Acceptable Target.

Anime and Manga

 * Sayonara Zetsubou Sensei takes this one to its logical extreme. Half the cast, or more, suffers from some form of severe mental disorder, which is usually played for laughs (albeit intentionally dark and disturbing laughs).
 * Alphonse and Edward from Fullmetal Alchemist display all signs of PTSD when confronted with their old teacher, who was a firm believer in Training From Hell. Naturally, we're supposed to laugh.

Film

 * Mr. Jones

Live Action TV

 * Scrubs usually plays right into this one for a cheap laugh but takes a long look at individual characters to find some genuine problems. This ranges from the psychologist's two o'clock client running into a shot just long enough to inform characters that "they've landed" to a surgeon unwilling unable to leave the operating room hours after performing surgery because he's still washing his hands.
 * This latter scene developed into a serious, very well done, and poignant scene in which the main character sees just how much the surgeon with OCD actually suffers because of his condition, while prior to this it had been played mostly for laughs.
 * As a kid watching Sesame Street, Forgetful Jones is quite funny. But when you look back at it as an adult, you are wondering what person thought it would be great to make fun of a man suffering from advanced dementia, who appears no longer be able to do anything unsupervised.
 * In a throwaway joke in Extras, Andy balks at the prospect of being set up with a woman with bipolar disorder and says something like, "She'll forget to take her lithium and kill me." Granted, he is an Unsympathetic Comedy Protagonist, but still.
 * In Glee, Emma Pilsbury's OCD is mostly shown as a strange character quirk instead of the debilitating mental illness that it is. The show also keeps making jokes about how Emma's OCD and germphobia has caused her to be a virgin at her age, as she can't make herself get intimate with people. It took until the end of season 2 for the show to actually treat her OCD seriously, by having her go to a therapist to get help, at which point she admits that she's actually ashamed of it and that it's basically destroying her life.
 * In one episode of CSI, Grissom befriends the schizophrenic sister of the victim, who was driven insane by the same circumstances that led to the vic's death and is now a rambling bag lady. The end of the episode shows Gris walking next to the sister as she pushes her cart, having a lovely and surprisingly philosophical conversation with her regarding her delusions (she believes she's searching for something important, and when she finds it she can finally rest).

Web Original

 * On the humour website Something Awful, Asperger's Syndrome is apparently considered a great punchline, and this is starting to catch on in other places around the web. At least some of the humour is derived from the tendency of non-professional internet denizens to self-diagnose for the condition, as a way of stating that social ineptness is not their fault. Obviously, it takes more than just social ineptness to be diagnosed with Asperger's, but that doesn't stop the self-diagnosers from leaping to conclusions.
 * Too bad that those goons aren't actually preventing people from self-diagnosing: they're just shaming who actually have Asperger's into silence.
 * Not to mention it's gotten very hard for people with actual AS to be taken seriously. Bad enough to repeatedly embarrass yourself despite trying your darndest not to; worse to have people not believe you when you say they were honest mistakes because AS is "obviously" just a fad diagnosis... me, bitter?
 * Often people who really were diagnosed with Asperger's even call the self diagnosed people too crazy to really have it.
 * Not all of those who are self-diagnosing are doing it to be assholes, though. Some are doing it because they really think they might be autistic, but are unable to get a diagnosis for some reason. (They insist on having someone there who witnessed your development because autism is a developmental disability and the person might either not have them or else not be on good terms with them. Alternatively, they might not be able to afford to see a psychiatrist)
 * In the Whateley Universe, there's a disease that some mutants have. Diedrick's Syndrome. It makes the sufferers sometimes break down into 'crazed supervillain' ranting and such. The best-known case at Whateley Academy is a popular target of the school bullies and elitists.

Western Animation

 * Ren from The Ren and Stimpy Show is probably the most famous example from Western animation. However, unlike most examples, his psychotic freak-outs weren't always played for laughter. While he did display Insane Equals Violent behaviour, it was always when he was being normal; when his manic side was triggered, that's when he snapped into batshit terrifying, yet non-violent mode. Examples include "Stimpy's Fan Club", in which a quite long and elaborate scene is dediacted to him considering killing Stimpy (complete with rambling that "his hands are dirty, the dirt won't come off" and that "with these hands, he holds the fate of millions"), but he doesn't lay a finger on him throughout all of it. There's also "Sven Hoek", in which he becomes furious with his cousin Sven and Stimpy, leading to another disturbing monologue. It truly gives a twist to Ren's personality, at least before he was flanderized post-season 2.
 * In My Little Pony Friendship Is Magic, the fandom seized onto a background character with 'derp' eyes, dubbed "Derpy Hooves". She became so popular that she made it into the show- with slurred speech, destructive tendencies and other traits, which combined with her eyes, made her seem to have a mental condition. People reacted badly to the portrayal as being offensive to people with genuine mental disorders as well as clashing with her fanon portrayal.
 * One thing to point out is that there was mixed reaction. Many people reacted positively to Derpy's portrayal, and some reacted negatively (though it is believed by some to be the work of trolls). In any case, the episode that gave her the spotlight was quickly changed to take out the derp eyes, not call her by name, and have her speak in a more generic tone of voice. However, Derpy has continued to make background cameos with no such backlash, even after the incident.
 * Read It and Weep has Screwloose, a clearly insane patient in a mental hospital, literally barking mad.
 * The Ice King of Adventure Time was first viewed as a nutjob, until it was revealed that his crown warped his mind to a point of no return, resulting in his fiance leaving him.
 * Lemongrab definitely qualifies. While he is clearly despised by everybody in the show for being a huge jerk to everybody who disagrees with him, viewer reaction ranges drastically from puzzlement to amusement to outright hatred to sympathy. While he is a mean, sour person, the cause of his bitter personality and anxiety is some kind of mental disorder that resulted from a failed experiment. He has anger management problems, an inability to read social cues, and doesn't think entirely logically, which isn't his fault. In-universe, he's treated like the jerk he is, but it's never taken into account that there is something seriously wrong with his brain.
 * The Royal Tart Toter. Mother of Glob, the Tart Toter. It's outright stated that he's insane and has completely lost touch with reality, but this is quickly swept under the rug and never brought up again. Jesse Moynihan even drew parallels between the Candy Kingdom Society and America during the Regan/Ron Paul years, in which mental hospitals were shut down, resulting in "a bunch of tart toters running around today in the streets."

Real Life

 * For much of human history, any behavior frowned upon by the majority or elite was considered to be a sign of mental illness-- and before this, evil (e.g. association with the devil, demonic possession etc.) Example: Drapetomania, a common mental illness among 19th century American slaves that irrationally compelled them to run away from their owners. However, it was considered easily treatable by flogging.
 * And in the Soviet Union, being opposed to Communism was considered a sign of mental illness, as well-- and was used as a thin veil for torture in "mental hospitals," disguised as "treatment."
 * And not only in the Soviet Union; Hitler's first euthenasia victims were 28 mental patients, while the United States likewise sometimes classified non-conformity to various legal requirements as mental illness-- and subjected victims to similar treatments, despite later being proven wrong.
 * In Western countries, homosexuality was considered a mental disorder up to the '70s.
 * In modern America, teens who disobey their parents are often diagnosed with Oppositional Defiant Disorder.
 * Evidently, and unfortunately, the use of the word retarded as a pejorative term or insult, even among "normal" people (subconsciously implying inferiority and stupidity as compared with mental retardation), is still common vernacular even on this very site, and in genres like Dead Baby Comedy.
 * That's just the latest term in a long line thereof. "Idiot" was a medical term once.
 * Even earlier than that, "Idiot" was a political slur that meant a person who was uninterested in public affairs.