Freakier Than Fiction

Sherlock Holmes: "Depend upon it, there is nothing so unnatural as the commonplace."

—A Case of Identity

Thus, God can work with the most mindbending coincidences, far-fetched plot devices, and perverse dramatic ironies, never giving a moment's thought to whether or not his audience will buy it. You do not have that luxury.

—How Not to Write A Novel

Originating in the Mark Twain quote that "Truth is stranger than fiction, but it is because fiction is obliged to stick to possibilities. Truth isn't.", no matter how weird, freaky, or squicky fiction gets, there will be something in Real Life that is even weirder, freakier, or squickier.

When such a thing is reported to other people, it will include a "Not Making This Up" Disclaimer because Reality Is Unrealistic and we really cannot, or do not want to, believe it is real.

When such a thing is adapted to fiction, the producers will be sure to protest, "The Tasteless But True Story!" These adaptations are usually just Very Loosely Based on a True Story, and so the original real thing probably still fits this trope.

Not to be confused with Stranger Than Fiction, which is a movie.

A subtrope of Truth in Television and of Ripped from the Headlines.

Examples of Freakier Than Fiction include:

Film

The film The Magdalene Sisters depicted the plight of girls sent to live in convents as washerwomen for the crime of being pregnant out of wedlock - or even for being accused of being "flirtatious"; many inmates were still virgins. The film actually toned down the habitual violence the girls endured under the nuns's hands and also showed the girls speaking to each other and forming friendships - in reality, both were forbidden...
In Singin' in the Rain, Cosmo says of film star Lina Lamont: "She can't act, she can't sing, she can't dance. A triple threat." Now, who in Real Life would build a musical around a Hollywood star who couldn't sing, dance or act? That would be the producers of a musical revue titled Two's Company, which opened on Broadway the same year Singin' in the Rain was released. What critics had to write about Bette Davis's leading performance resembled the movie's put-down of its fictional actress.
The film Changeling ran into this trope. It was, in fact, based on a true story, but nobody would believe it...when it was, in fact, not exaggerated in the slightest. So Stracynski added sources to the script and such, to prove it was real! Not only that, but many of the more bizarre and freaktacular parts of the serial killer's exploits were left out, as they distracted from the main story. During the DVD extra, Clint Eastwood noted that if it were fiction, no one would believe it.
WWII hero Audie Murphy played himself in the movie To Hell And Back, based on his autobiography. During the adaptation, he requested that certain parts of his exploits (like the time he had malaria, but still managed to single-handedly hold off hundreds of Germans and half a dozen tanks in a single tank of his own, without the tank moving because he was running it solo, while it was on fire) be watered down a little, since nobody would believe the real thing.
Descriptions of Jørgen Haagen Schmith's last stand (also his first stand, since he was the driver) are considerably more amazing than the version of events shown in Flammen og Citronen.
The actual events that inspired the film 300 were much worse than displayed. Rather than just kick the messenger into a well, the Spartans dressed up pre-pubescent boys as girls and gave them to the messengers for entertainment. The boys then proceeded to kill the messengers when one of them molested one of the boys...
- That was Young Alexander of Macedonia who did that. The Persians told the Macedonians that it was a common courtesy (Most likely a lie anyway, but Persia was extremely powerful back then) to give messengers their finest women (they also asked the Macedonians for Earth and Water). Young Alexander objected to this, so he did what is described above.
- The film also neglects to mention that the Spartans were just as much of a genocidal, perverse faction as the Nazis. Some sources even claim they were worse. Of course, the ending reveals the whole thing was in-universe propaganda with an Unreliable Narrator for the Spartan's own benefit.
Obviously, the events of the film Apollo 13 actually happened. But what they don't mention is that there were several additional malfunctions, and one or two of the events mentioned in passing in the movie were actually critical problems in reality. There were removed/downsized because, yes, producers thought no one would believe it.
- No one in the Apollo program at the time would have believed it either had it not actually happened.
- Also, some test audiences reacted poorly to the ending - saying it could never happen and was totally unrealistic.
Frank Abagnale's last escape could never have been included in Catch Me If You Can due to being even less plausible than tunneling out of a landing airplane. That solitary cell in federal prison? He allegedly conned his way out by pretending to be an undercover FBI agent.

Literature

New York writer Paul Auster finally got tired of people telling him his stories were unrealistic (in fact, a lot of them deal with coincidences and unlikely events of all sorts). So he encouraged the audience of NPR to write up their own stories. Only condition: the story had to be true. The result is available as a book ("I thought my father was God").

Live-Action TV

Law & Order gets its plots from somewhere. Such as the case of Colleen Stan.
An episode of House ("Alone") references the real-life case of Whitney Cerak and Laura Van Ryn where two girls were in an accident, one killed and one surviving but too injured to identify herself, and the surviving and dead girl's identities were switched.
- CSI New York also based an episode around this story, with an added twist: the spiteful mother of the "dead" girl smothered the survivor before the switch was discovered, ultimately getting her arrested for murdering her own daughter.
The Supernatural episode "No Exit" featured the ghost of the United States's first documented serial killer, one H.H. Holmes. Holmes's actual exploits—which included building a "murder hotel" whose guests sometimes didn't check out—can be read about in Rick Geary's Treasury of Victorian Murder series and in the book The Devil in the White City. And yes, his tomb was sealed in concrete.

Theatre

The playwright behind 1776 had to leave out actual quotes by the Founding Fathers (such as John Adams' prediction that not taking care of slavery then and there would cause trouble in a hundred years) because no one would believe he wasn't using authorial hindsight.

Video Games

A popular Nintendo DS videogame series also references the real-life case of Whitney Cerak and Laura Van Ryn (described under Live-Action TV). Of course, the Ace Attorney series bought in actual mediums to talk to the dead, which is what drives the surviving sister to murder.

Web Comics

Saturday Morning Breakfast Cereal goes out of its way to disprove this, using a variant on the proof that there is no greatest positive integer. Basically, take the strangest thing that exists in reality, then add a monkey with Hitler's face to it to get something even stranger, yet fictional.

Web Original

"Poe's Law" often comes up in discussions of religious fundamentalism online. The Law states that it is difficult to prove, without a smiley or other blatant evidence of sarcasm, whether someone is a legit religious nut or a parody of religious nuts, because no matter how crazy a parody might sound to the parodist, there's an actual religious nut out there saying something similar to the parody. (It has nothing to do with Edgar Allan Poe, in spite of the fact that people who think a fundy is fake will post pictures of Poe to say they're calling Poe's Law on it.) It's not just limited to religion, either. Fandom, politics, even pizza toppings [citation needed].
Cracked.com is practically in love with this trope as much as boobs, writing humorous articles on true stories and facts that seem utterly ridiculous half the time even though it's real.
- To be fair, in their attempts to make the stories "humorous", they tend to distort the facts or take them out of context so much that they might as well be fictional anyway.

Real Life

BTK Dennis Rader, of Wichita, Kansas, has probably been the basis for several fictional serial killers. He would have gotten away scott-free, right under everyone's nose, too, if he hadn't decided to get himself caught twenty years after the fact by stalking the local newspaper and the detective who was head of his case way back when. His crimes were horrifying, but his reported beliefs about the afterlife were worse: he thought his victims would be his eternal slaves. His pastor, who sat through the trial up to this point in demonstration of the belief that even killers could be achieve salvation if properly repentant, stood up and walked out.
WWII in general would make a terribly, terribly implausible TV show.
The world's most proficient sniper, Simo Häyhä AKA "The White Death", has 700 confirmed kills. Yes, seven hundred. All achieved in about three months in far less than optimal conditions. The Other Wiki has more information on the guy, but needless to say, if he was fictional, this would be considered ridiculous if it was played for anything other than laughs.
The Con Lang community uses "ANADEWism" to refer to things that A Natural language has Already Done Even Worse.
Cargo cults