Offscreen Reality Warp

When the camera is looking at a certain scene, cuts (or pans) to another scene, but then cuts back to the original scene to show that things have inexplicably changed in the short amount of time that has passed, faster than would be possible.

Sometimes may manifest even if the camera does not move; instead, some object will obscure part of the scene, and when it moves, the scene will have been changed.

To give a hypothetical example: A character is dressed in certain clothing. The camera cuts away for a second then comes back to the character, showing him in completely different clothes, despite the fact that it would've been impossible for the character to have actually changed his clothes in such a short amount of time (sometimes this impossibility might be enhanced by showing the character in the same position). Cue shock/disbelief from other characters.

This trope isn't about production goofs or continuity errors; rather, this is done intentionally. When played for laughs, the changes are often absurd or improbable. Occasionally is played straight to imply that something supernatural has happened, or a literal reality warp.

A related trope is Offscreen Teleportation, where a character can change position far too quickly while offscreen. Compare Instant Costume Change. Related to Stealth Hi Bye, where a character appears or disappears in the short time it takes the camera to swing away and back again. All these are made possible by Behind the Black.

See also Gaslighting, when characters do this to each other while the other is sleeping.

Examples of Offscreen Reality Warp include:

Comics

An ~~Offscreen~~Off-Panel Reality Warp: Alan Moore once wrote a one-shot strip called "Dr. Dibworthy's Disappointing Day" for 2000 AD. In order to test whether a device designed to send small objects back in time really does just that, Dr. Dibworthy decides to send an object back to a point in time where its presence would actually change history and, by virtue, the present as well. He decides to send a flat-iron back to brain an obscure Turkish diplomat in the 11th century. The next panel reflects Godwin's Law of Time Travel while the Doc notes, "Nothing happened." Then, he decides to drop an anvil on King John just before the signing of the Magna Carta. Again, the next panel reflects striking changes to the present while the Doc notes, "Nothing happened." Finally, he decides to test his device by stopping the Primal Atom from exploding (i.e., preventing the Big Bang from happening). Nothing happened.
Lampshaded in a Garfield comic where Jon demonstrates that he can't even leave Garfield and Odie alone for a second. After he is outside for exactly one second, he returns to find his house completely trashed.

Film

One rather scary example in Poltergeist: When Diane and Carol Anne were in the kitchen, the chairs were around the dining room table as usual. The camera looks away for a moment, and when it returns, the chairs are all stacked up on the table — put there by the ghosts.
Similar to the Poltergeist example above, there is a scene in The Sixth Sense where Cole's mom turns to perform some brief task, and returns to find every single cabinet door open around Cole. Cole himself has not moved, but is visibly freaked out by the event.
- in both cases, the scene is done as a single Long Take, to make it extra freaky to the viewers as well
In one of the Scary Movie movies, a police officer's hat increases in size between shots. It's probably the best part of the movie.
A Running Gag through The Great Race is that Maggie Dubois never wears the same outfit twice. Occasionally they take this to ridiculous extents as she'll have on an entirely new elaborate wardrobe about 5 seconds after we last saw her, in a scene which clearly has no time jumps.
At the end of Dogma, God looks over the carnage that Bartleby and Loki caused, then smiles, and (after a quick cut to a Reaction Shot from the others), everything is back to normal.

Literature

The house in House of Leaves likes to do this in subtle and not so subtle ways: a new door here, growing slightly Bigger on the Inside there, naturally driving the inhabitants crazy when they start noticing it. Since the manuscript about the house in the book describes the contents of a documentary film, this also fictionally happens in an actual film (which is true within the fiction within a fiction that may not really be fiction in the first-level fiction), making it even closer to the way the trope is usually played, although at this stage of Mind Screw one might not be certain what the heck we're talking about any more.

Live Action Television

A Saturday Night Live bit was an infomercial for a microwave oven that, for some reason, uses tachyons to cook food. As one host puts a turkey into the oven, the other host wonders about the consequences of faster-than-light travel. The camera then cuts to an infographic while the announcer warns that the oven may cause time travel, and that if time travel occurs, not to change the past. The camera then cuts back to the hosts, who are now in different clothes and with different hairstyles. The bit continues along in this vein, and the reality warping gets worse (read: hilarious) each time.
There was a Benny Hill sketch that was built around this. They were filming a movie with Benny as the romantic lead. Continuity errors abounded, including changing scenery, costumes and even actors (such as Benny being replaced for one Over the Shoulder shot by a greasy lothario type).
There is an episode of Samantha Who? where Sam gets a (badly-behaved) dog. She leaves the animal and her flatmate sitting on the sofa while she goes out. Realising she has forgotten something, she steps back through the door a second later and finds the pair sitting in exactly the same positions, only the sofa cushions have been torn to pieces and the apartment is covered in stuffing.
The Buffy the Vampire Slayer episode "Selfless" has a flashback to a (previously-unseen) scene during the Musical Episode, with Anya singing a song about getting married to Xander. Near the end of the song she steps through a doorway and comes out on the other side wearing a wedding dress.
Lampshaded in an episode of A.N.T. Farm where Chyna notices a Lady Gaga parody changing her outfit to an equally ridiculous one every time she goes off and comes back on screen.

Western Animation

On one episode of Duck Dodgers, Dr. I.Q. High leaves Dodgers in charge of his home. The doctor is about to go into his car when he realizes he forgot his keys, so when he turns back to get them, he finds his home burnt to the ground. Dodgers then tells him a preposterous story that would have taken far more time than it took Dr. High to go to his car and back.
Lampshaded on The Simpsons, in the episode "Bart's Inner Child" where the family gets a free trampoline. After realizing the dangers of the trampoline, Homer tries to get rid of it but is unsuccessful. Bart simply chains the trampoline to a pole with a bike lock and tells Homer to turn around and count to three. They both do so, then glance back and see Snake already using a bolt cutter on the chain. Bart quickly turns back around with Homer and says, "Better make it five..."
- In another episode, Marge makes everybody clean the house before going out. A sparkling clean kitchen is seen through a swinging door, which swings closed and then open again... to reveal a ridiculously over-the-top mess of a kitchen.
- When Marge is in jail, Lisa says they can keep the house tidy if they all do their part. Homer and Bart are unenthusiastic. Cut to "Five minutes later", and the kitchen is absurdly messy, falling apart and occupied by alligators.
The SpongeBob SquarePants episode "Jellyfish Hunter" has Mr. Krabs send SpongeBob out to catch jellyfish. "And make it..." (SpongeBob has already returned with jellyfish) "...quick."
Phineas and Ferb, all the time. Obviously, the title characters and Dr. Doofensmirtz do it when creating their inventions, and sometimes Perry The Platypus does it in his battles with Doof, but everyone else (especially Candace) can pull off absurdly quick feats if it advances the story or is funny.
In one episode of The Grim Adventures of Billy & Mandy, Billy, after unearthing and thawing out Fred Flintstone who was encased in permafrost, goes into his kitchen and asks Fred not to destroy the house while he's gone. He sticks his head out to ask Fred if he likes chili on his cereal, after which it is shown that Fred trashed the living room and is still in the exact same position he was when Billy left.

Web Original

Dr. Horrible's Sing-Along Blog: The titular Doctor does this in Act I. He ducks behind a concrete wall with his duffel bag, while singing, and pops back up a half-second later, having changed from civvies to his supervillain outfit and continues the song on the same note he left it. The DVD Commentary notes that, in actual production, it took long enough for Neil Patrick Harris to change costume that there's a noticeable light shift in the set if you look closely.

Real Life

A study in awareness once did this as part of an experiment—subjects spoke with a clerk behind a counter and at some point during the conversation the clerk would duck down behind the counter, ostensibly to retrieve a form. The person who stood back up was in fact a completely different person wearing different clothing, but only a minority of the subjects noticed.