Déjà Vu, literally "already seen" in French is a sensation of having already lived through what's currently happening. In real life, it's just a regular anomaly of memory recall. In fictionland, it's a sign that something isn't quite right.
Commonly experienced by characters who are starting to realize they are part of a "Groundhog Day" Loop. Occasionally appears in Time Travel plots. Truth in Television and a source of Paranoia Fuel in Real Life. Related to A Glitch in the Matrix, Deja Vu may be a symptom of encountering that trope. May be triggered by passing through a Door to Before. Sometimes used for an Oh, No... Not Again! gag.
- Mushishi: One chapter involves Ginko meeting a man who is lured by a mushi, that causes him go through a "Groundhog Day" Loop over and over. The result being the man is constantly having a lingering feeling of deja vu, but since the loop begins at his childhood he doesn't remember what is causing it.
- The Matrix: Neo experiences deja vu after seeing the same cat go by twice. The rest of the cast go on alert, as deja vu is a sign of a recent change made in the program, causing A Glitch in the Matrix while the agents patched it.
- Déjà Vu: Despite lending the movie its title, this doesn't occur until the end of the film when Denzel Washington's character seems to recall the memories of his temporal duplicate who died just before he showed up.
- A Monty Python's Flying Circus sketch involves a show exploring the concept of deja vu. Suddenly the sketch starts over, and by the third time it happens the commentator starts to notice something is wrong.
- Star Trek: The Next Generation: In "Cause And Effect", the crew are caught in a "Groundhog Day" Loop, Doctor Crusher begins to experience Deja Vu and so do the other crew members when she brings up the issue.
- The Far Side. A hippie stops at a house to ask for directions; upon noticing that the person he's speaking with is an elephant-bird-giraffe-man, he says, "Oh, wow, deja vu."
- Last Unicorn Games' Star Trek RPG supplement All Our Yesterdays: The Time Travel Sourcebook. When people are caught in a temporal loop (a "Groundhog Day" Loop where no one remembers that they've gone through it before), they will sometimes get a feeling of deja vu.
- BioShock: One of Andrew Ryan's taunts over the radio hints at Jack experiencing this. Rapture is oddly familiar to Jack because he's a Laser Guided Tyke Bomb grown in the city and sent to the surface, programmed to return and kill Ryan.
"So far away from your family, from your friends, from everything you ever loved. But, for some reason you like it here. You feel something you can't quite put your finger on. Think about it for a second and maybe the word will come to you: nostalgia."
- In the Marathon Trilogy, in the first game's manual, as the our Hero escapes into the escape pod he ponders this: "Oddly, this is familiar to you, as if it were from an old dream, but you can't exactly remember...". Not much comes of it until the third game, where the plot is centered around saving the reality from getting eaten by a Cosmic Horror, and it involves dream-themed dimension jumping/time-travelling trying to prevent the release of said Cosmic Horror.
- Max Payne: Max experiences this in the original game—while having a bad Valkyr trip. In his hallucinations, he enters a room with a ringing telephone. When he picks up, he hears only gibberish and puts it down. However, the next room he enters looks exactly the same, and the voice on the phone tries to tell him he has been drugged—to which he declares that he only hears gibberish and puts the phone down.
- Metal Gear Solid V: Ground Zeroes features a DLC episode named after the concept which is formed by a series of Call Backs to the original Metal Gear Solid, even allowing you to play as the protagonist of that game.
- In Penumbra: Black Plague, feelings of deja vu are one of the early symptoms of infection by the Tuurngait virus. The first time you learn this, this particular bit of info is repeated twice, presumably to unnerve the player. And it's fitting, as the player character is already infected.
- In Undertale, characters have déjà vu-like memories of the events that happened before the player reloaded the game. Except for Flowey, who can fully remember them. Sans has learned that someone is messing with the timeline using SAVEs simply by being very perceptive.
- In Homestuck, this is a telltale symptom of entering a Dreambubble. The sense of Dejá Vu only increases until the dreamer realizes that they're merely recalling a memory.