Mistaken for Apocalypse

Usually a comedy trope. A character (or a group of characters) wakes to a series of unusual circumstances, such as an absence of people/empty streets, destruction of property, phones/internet being down, etc. He then interprets all these signs as meaning an apocalypse occurred while he was sleeping/distracted, and that he is the last man left alive.

He then acts on this usually in one of two ways:

Start trying to survive, gathering food, building a fort, etc.
Act with a complete and total lack of inhibition, doing everything he's always wanted to do without consequences.

As it turns out, however, he isn't the last man alive. In fact, no apocalypse happened at all. Everything that's convinced him that humanity has been wiped out were merely coincidences which he misinterpreted.

If his misinterpretations weren't due to his own stupidity, it will then turn out that someone tricked him into believing this.

If this isn't being Played for Laughs, then the other person might have been trying to trick them as a means to get information from them.

Related to, and can overlap with, Faked Rip Van Winkle.

Examples of Mistaken for Apocalypse include:

Anime and Manga

Happen in a rather long story in Doraemon. In short, Nobita found that in the near future there is no one in the neighborhood and several ant-like aliens roam it. Thriller adventure ensued, but after everything is done (by sheer dumb luck!), it turns out that everyone is just watching a movie shooting session featuring a famous actress somewhere else.

Comic Books

In the Italian comic Cattivik in one episode the main character thinks that a nuclear war or a similar disaster happened and forced everyone in the sewers. After two seconds of apparent Angst, he decides to go out there and steal everything left.
One of the stories in XXXenophile used the "trick for others" version.

Film

Blast from the Past - A plane crashes into the Webbers house while they're touring their new fallout shelter underground. Believing World War III has broken out in nuclear war, they spend the next 35 years in their shelter waiting for the radiation to clear. Even after leaving the shelter and visiting the surface, they continue to believe they're in a post-apocalyptic world, including mistaking a transsexual hooker for some kind of mutant.
Gamera Vs. Zigra has a loony bum telling the children it's a post-apocalyptic 1985 (the film was set in 1971) and that the Great Lord Miyamuto has come back.

Folk Tales

Chicken Licken/Henny Penny/Chicken Little gave us the famous "The sky is falling!"
- Averted in the Disney movie, Chicken Little, where it's more about Cassandra Truth / Crying Wolf.

Live Action TV

My Name Is Earl - In a flashback episode taking place on New Years 2000, the gang learns of the Y2K bug, and - due to a series of coincidences and misunderstandings - believe that the machines rose up and wiped out humanity, except for them. They then go live at the local department store and form a new society based around making decisions with a "Take-A-Number" machine.
In the short lived Animal House TV series, the Omega house hides in their underground bomb shelter during the Cuban Missile Crisis. Delta House decides to mess with them and while Omega is looking through the shelter's periscope, Delta shoots a camera flash at it. Then they put smoke around it. When the smoke clears, Omega sees a fake diorama of the ruins of Faber College through the periscope.
Mission: Impossible TOS episode "Two Thousand". A nuclear physicist steals 50 kg of plutonium. The IMF team tries to convince him that the United States was devastated by a nuclear war and he has been in a coma for 28 years.
- There's another episode where the IMF trick some spies into thinking their country has nuked the US, just so they can steal the spies' codebook.
In an episode of Six Feet Under, a wacky circumstance involving helium-filled blow-up sex dolls leads a woman to think the Rapture has come - she runs out into the street and gets hit by a car.
In an episode of the 1980s Twilight Zone a guy who's paranoid about nuclear was builds himself an underground shelter. While he's showing a visiting friend around there's what looks like a nuclear explosion, and he seals them both in for weeks. When he believes the radiation will have died down a bit he sends his friend out to take a look. The friend reports that it's pitch black, suggesting a nuclear winter, and everything's been reduced to rubble. The shelter guy leaves his friend outside to die rather than let him back in to contaminate the shelter, but he knows his own supplies of food and water won't last forever.

Meanwhile... just a few miles away the sun is shining and the birds are singing. The entire district containing the house with the fallout shelter was sealed in a concrete dome following a nuclear accident which was thought to have had no survivors.

- Another episode of The Twilight Zone had an affluent man build a fallout bunker—and also faked footage to make people think that World War III had started. The reason for this is because he invited three people to his house that night: his schoolteacher from when he was a boy, a priest, and his commanding officer. All of them had disciplined him for being a terrible person, he wanted to see if they'd beg his forgiveness if they thought he was the only way they could survive the radiation. It turns out that he's still such a jerk that they all opt to not go into his bunker. He's so distraught that he later fantasizes that the apocalypse has happened for real, buying his own fake story.
On 3rd Rock from the Sun, Sally thought the world was ending the first time she saw snow, especially as it was followed by a blackout. As she was alone with Dick's clueless student Leon at the time, she explained to him that the world was ending and they would have to copulate as much as possible. He decided to let her think that, but unfortunately for him, the lights came on just as they were about to go at it.

Literature

This happens in a SpongeBob SquarePants book.
The Hank the Cowdog book "It's A Dog's Life" had Hank, through a false report from Drover, think that the world was going to end on Tuesday.
There's a short story in which a young man who spends too much time on the internet has it go out (and there's sunspots or something causing his other communication devices not to function) and immediately jumps to the conclusion that World War Three is about to happen. Rather than warn anyone, (the character believes himself of superior intelligence and all his neighbors idiots) he heads for the hills, and dies because he doesn't know anything about wilderness survival.

Video Games

In Oblivion, a quest given by Sheogorath (the Daedric Prince of Madness who enjoys screwing with mortals for fun) involves convincing a local town the apocalypse is at hand by producing signs foretold by a prophecy, one of which is a rain of burning dogs. (Funnily enough, the apocalypse is actually at hand, although it has nothing to do with burning dogs or the town's prophecy.)

Puppet Shows

On The Muppet Show, Scooter gives Beauregard a tarot reading which foretells the end of the world. At the end, it is revealed that Scooter read the cards wrong; they actually said that your laundry will come back dingy.

Western Animation

Duckman - As the city prepares for a city-wide disaster drill in a large underground bunker, everyone Duckman comes in contact with tries to remind him of it. Unfortunately, in every case something drowns them out, interrupts them or Duckman outright ignores them. When the drill happens, Duckman misses it due to stumbling around in a bondage mask. Seeing the streets empty, Duckman assumes everyone is dead and immediately starts looting. He meets a deaf-mute woman who was busy doing a gymnastics routine when the drill happened and also assumed the world ended. Together they rampage through the streets and ultimately destroy the town before the people return from the drill.
American Dad - Arriving late to a CIA nuclear attack drill, Stan is told that it is "100% real" by his boss and hurries home to take his family to safety in the woods. After realizing it was fake, Stan keeps up the charade anyway so as to not be thought of as a fool, and continues to let his family believe the world has ended.
In an episode of Futurama, Fry and his girlfriend refreeze themselves in the year 3000 expecting to wake up in the year 4000. They find themselves in what appears to be a post-apocalyptic ruined New New York. Turns out it's still the year 3000, and they're in Los Angeles. There was no apocalypse; L.A. is just like that.
In one South Park episode, Cartman tricks Butters into thinking a giant meteor has crashed into the Earth. Butters then hides out in the local waste dump while the town searches for him.
In The Amazing World of Gumball, Gumball and Darwin misread a series of coincidences as signs that the world will end during a solar eclipse in 24 hours. Gumball tries to do all the things he always wanted to do, while his father Richard - the only other person to believe them - goes in full survivalist mode.
There was an episode of The Adventures of Jimmy Neutron where this happened to Jimmy's dad.
In an episode of Rugrats the babies and Angelica thought that the sky was falling.