Somebody thought they were protected by the power of narrative convention. Then reality ensued.
This can sometimes be seen on the hard end of the Sliding Scale of Idealism Versus Cynicism, though it isn't necessarily so since realism, despite what many claim, is not the same as cynicism.
Generally, this trope is not used in order to make fiction completely and entirely mirror mundane everyday life. Except when it is. This is also surprisingly often used as a Comedy Trope. Contrast Fantasy All Along, when reality ensues and immediately afterwards fantasy kicks in again.
Warning: As this trope frequently occurs at the climax of a work, spoilers are likely to be unmarked. Caution advised.
Sprite's "Obey Your Thirst" campaign in The Nineties was a series of commercials based around subverting and mocking the tropes of advertising by invoking this trope.
One of the most famous was the "Grant Hill Drinks Sprite" series of ads, which parodied Cereal Induced Superpowers. In one of them, a kid spots NBA player Grant Hill drinking Sprite, and thinks Sprite will make him a basketball player... which he quickly disproves by drinking Sprite and then attempting a slam dunk, failing, and falling on his ass.
Announcer: If you want to make it to the NBA... practice. If you want a refreshing drink, obey your thirst. Sprite.
Another one has a group of kids talking about Hill's athletic prowess and offering various hypotheses for it (his Brazilian rubber sneakers, his lightweight shorts, his shaved head) before one mentions that he drinks Sprite... only to say that he's merely not thirsty anymore after drinking it.
Similarly, a bunch of young guys drive around in a convertible in slow motion, bouncing the car on its wheels to look cool. The car stops, one guy leaps out out of the car and goes to dramatically chug back his Sprite. When he turns the cap, the bottle explodes and covers him in soft-drink — because all that bouncing shook it up. He does not look cool while shrieking and dripping wet.
Sprite's "Sun Fizz" ad, in which a stereotypical juice ad plays out with mother and children getting excited over Sun Fizz. A cartoon Sun Fizz mascot jumps out of the carton and rattles off his part of the spiel... prompting the entire family to run screaming in terror from the cartoon sun that should not be. Who gives chase.
A fake advertisement for a soft drink called Jooky ("the party in a can!") advertised it with images of people surfing, playing volleyball, and having fun on the beach, all to a faux-Caribbean jingle... before cutting back to show a pair of slackers watching the ad and popping open their cans of Jooky, all while a snowstorm rages outside. One of them accidentally breaks the tab off the can and is unable to open it.
Part of what makes it depressingly realistic are the cartoon kid's reactions to those injuries. Most victims of Amusing Injuries don't seem to particularly care that they are frequently and horrifically maimed totally at the whim of other, often-ill-tempered people - here, by the end of the commercial, the mere act of his father entering his room causes the kid to utterly panic.
There's a Dr. Pepper TV ad where two guys were moving a pinball machine down the stairs. A snapping noise has been heard and one of the guys is in pain. A doctor with a can of Dr. Pepper comes near the guy, complete with a Dubstep song. The guy seemed happy until he resumed being hurt and was about to let go of the machine, which would make the machine crash in a wall.
In a spoof of Hansel and Gretel, the witch is cackling to herself about how clever her plan is as she builds a gingerbread house to ensnare any little boys and girls who might pass her way. When Hansel and Gretel arrive sometime later...
Hansel: Egad, Gretel! Have you ever seen so many ants in your life? Gretel: Never! Say, Hansel, do you hear somebody screaming?
In a contrast between a movie cowboy and a real life one, the movie cowboy is hailed as a hero for defeating his rival in a fistfight, while the real life one is knocked out in one blow, wins by ambushing his rival at a later date, and is lynched for murder.
Another comic has an inexperienced race driver enter a 24-hour race in an old piece of junk of a car. Everyone laughs at him, but the plucky underdog takes chances none of the other drivers dare, pushes his car to the limit, wins the crowd over with his death-defying driving... and finishes dead last, because his car is a piece of junk.
In a parody of the airlines' safety instructions, Mad shows panels of what people would actually do in those situations- panicking, making mistakes and not following the directions. In one example, two people frantically grab oxygen masks, strangling the man seated between them, and in another, a swarm of people rush to the emergency exit.
This trope is bread and water for song parodies.
Swedish songwriter Lars Winnerbäck tells us what really happened to some of Astrid Lindgren's characters in his "Balladen om Konsekvenser" (The Ballad of Consequences). Pippi Longstocking is in jail for assaulting a police officer, illegally possessing a wild animal and recieving stolen property. Rasmus is a homeless alcoholic, Ronja is screaming her head off in a mental hospital, and Kato from Mio My Mioruns a mindless commercial TV channel.
The song "Scalp" by Atmosphere features the narrator describing his night. He goes to the bar and meets his friend Sonny, who offers to pay him for retrieving a package from a tattoo parlor. One expects the protagonist to follow through with his task, possibly finding something surprising in the package along the way, but instead he is killed in a car crash immediately after leaving the bar. Which is what happens when you drink $50 worth of alcohol and then drive at night.
In "Women Lose Weight" by Morcheeba, guest rapper Slick Rick tells us he's going to kill wife because she gained weight after he married her (as well as what a shame it is in general that women do this), then actually goes through with it by running her off the road. Reality ensues in the last verse when he's charged with her murder and realises that while it is important for a woman to remain desirable to her husband, her failure to do so does NOT justify murder.
Skrillex's Bangarangmusic video (Alternate link for German users, since Youtube blocks these video in Germany >:() features three cunning little boys robbing an ice-cream truck of its stock, complete with fat, cartoonish ice-cream man. The plan goes wrong and they end up seriously injuring the guy to escape. (He was going to use a stick to beat one, but there was no way they could see that.) When they grow up and become professional thieves, the one who accidentally cut off the ice-cream man's hand gives some of his loot to the guy by way of compensation.
Occurs in "Big Bad John" by Jimmy Dean. While John is a very strong man, strong enough to hold up a timber to save his fellow miners, he can't hold it up long enough for them to come back and save him.
Aaron Carter's "Aaron's Party" is about... well take a guess. At the end, his parents come home and he gets grounded.
The music video for the song Baby I'm Sorry by the K-Pop boyband MYNAME applies this rather brutally. At first, things look fairly standard, with a bunch of teenage boys beating up a group thugs with full on The Power of Friendship implications, token coward member aside. Then, two of them get involved in organized crime, and when a group member is killed on an assassination job, an attempt at a Roaring Rampage of Revenge goes horribly wrong. As it turns out, friendship, righteous anger and a coward finally finding the strength to fight aren't much good against guns and tougher, more experienced opponents. In the end, all our protagonists die horribly and painfully, one even crying for his mother as he goes.
Mythology and Religion
In The Bible, Moses sees an overseer whipping a Jew and is overcome with rage, killing him. Rather than immediately viewing him as an ally and savior, this makes the other Jews view him as a dangerous murderer — the next day, when he confronts one of the Jews about fighting with some other Jew, he asks if Moses is going to kill him, too.
Act one of The Fantasticks ends happily, with the couple together and the "feud" ending. Act two opens up with "This Plum Is Too Ripe", which is all about the characters realizing that everything isn't so great after all.
Into the Woods is all over this trope. Not only does it show the realistic consequences of fairy tales (particularly in regards to Fourth Date Marriage and Parental Abandonment), it also shows just how dangerous some fairy tale characters can be in a more realistic setting. When a giant comes down from the beanstalk, the audience goes "hey, cool!" at first, until she starts actually stepping on people. It's not played for laughs. However this only applies for Act II. Act I is frequently used for school productions, as it's a fairly straightforward mash-up of recognisable fairy-tales that ends with a musical number celebrating how all the heroes have had their dreams come true and now they're going to live Happily Ever After... and then Act II opens, and everyone is faced with the fallout of their decisions.
This trope is often taken as the reason for Hamlet's ambiguous reluctance to kill Claudius — in reality (and contrary to the Elizabethan revenge dramas that were popular at the time), most people simply wouldn't be able to live up to the command to put a knife in another person's back.
Urinetown takes place in a town where a drought has caused a terrible water shortage. A corporation controls the public toilets and forces people to pay to use them to control water consumption with harsh laws ensuring the townspeople comply. The poor people of the town eventually rise up and overthrow the corporation, changing the law to allow people to use the toilet for free… only for the remaining water supply to quickly be used up and causing most of the population to die from thirst.
Despite passionate pleas, Masayuki in A Profile is ultimately completely unable to make Miou's parents reconcile. As he says to Miou, it's not like a kid like him can do much to convince adults of anything serious like that. On the other hand, it's not completely without results in that it made her father approve of him, whereas until then he was judging Masayuki as the street punk he used to be.
Rewrite despite being a Key work where everything works out eventually features this. For example in Shizuru's routes Kotarou effectively acts as the millstone for Shizuru who is one of the strongest fighters in Guardian, an organization built to stop salvation from happening. As a result of this, salvation ends up taking place more or less annihilating humanity.
Umineko no Naku Koro ni can be argued to be this. While the conflict between mystery and fantasy is an important aspect of the series, the real conflict is between mystery/fantasy and reality. This can be easily be seen in Ep 2 with the locked chapel where the real trick is the simplest one, namely that Rosa lied (in accordance to Yasu's script) and it was never locked at all. It can also be seen in Ep 7 when the adults find the gold and instead of showing a series of mystery/fantasy scenes we are instead shown what would happen in this type of family in such a situation: a lot of shootings and deaths.
Ace Attorney has a few moments where legally valid real life objections, and courtroom rules that'll hold up in an American court, are used. Since the court system in game is so insane, it's a bit jarring when they do this. (The games are based on the Japanese system where it's a more accurate representation)
For example, the Judge at one point tells a witness that her testimony is hearsay and therefore isn't admissible. Although this is immediately shattered, when the prosecutor objects to the Judge himself, stating at the testimony should be accepted. Phoenix himself, however, goes on to use hearsay to his advantage later on.
Judge: Mr. Wright, please keep the questions for the witness.
Phoenix: "Something you heard from someone else isn't admissible as testimony". Your words, Your Honor.
Judge: ... Touche, Mr. Wright.
We also see characters who commit crimes not related to the murder being investigated (altering crime scenes, forging evidence, wiretapping, interfering with investigations, attacking police officers, etc) shown in the detention center later, showing that they do serve time for what they did. On the other hand, it seems darned near impossible to actually get anyone in trouble for perjury.
Katawa Shoujo deconstructs a lot of the typical eroge/harem game tropes, with the standard character archetypes being portrayed and treated much more realistically. Hanako, the Fragile Flower, seems like she needs protection and a shoulder to cry on, but in reality she resents her friends for treating her like she can't handle herself. Rin is a Cloudcuckoolander with all of its typical behaviors, but it turns out that such behavior is not always funny or cute, and makes it very hard for the person to express how they feel to others.
School Days shows what can happen if you try to balance the affection of multiple girls, and what kind of effect that can end up having on the girls. It can make them want to stab you with a kitchen knife and/or a katana.