Mundanization

Putting the cast of a (relatively) fantastical setting into a contemporary, "normal" one. The entertainment often comes from the incongruity of not fitting in or the fact that we're seeing the characters in a realistic setting.

Exemplified by the famous and much enjoyed Star Trek episodes where characters either go to the past or get involved in a holodeck novel, and (in practice) leave their show's tropes behind a bit.

However, doing this as a Genre Shift (or a Retooled series's whole premise) is often too obvious to be successful.

If it involves people from a futuristic setting travelling into the past (or a recreation of it), expect there to be a Fan of the Past who provides exposition or takes charge.

Compare Brought Down to Normal, Refugee From TV Land, Universal Adaptor Cast, Welcome to The Real World. See also Transplanted Character Fic and High School AU for Fanfic version of this trope.

Anime & Manga

 * One of the ending sequences for Naruto: Shippouden drops the cast into a High School AU.
 * The whole point of Neon Genesis Evangelion: Angelic Days, a shojo manga that extracts the Mind Screwy, psychological, post-apocalyptic elements of NGE that we all know and hate to love in place of a light, romantic-comedy high school setting. With Evas in the background.
 * Along the lines of Tale Spin, Kino's Journey has a spin-off called Gakuen Kino. The latter is, admittedly, a High School AU with magical girls and random monsters floating around, but given that Kino's Journey is a poster child for surreal magic realism, it seems to be a good borderline example.
 * Gurren Gakuen-hen is another official High School AU, this one for Tengen Toppa Gurren Lagann. As with Neon Genesis Evangelion, the alternate universe briefly appears in the original show in the form of a dream or hallucination.
 * You're Under Arrest has a dream episode where Natsumi becomes a detective in Heian-era Japan, centuries in the past, with the entire cast re-cast as the townspeople. (There is an immensely-popular Japanese live-action TV show about a detective in the Heian Era, and Natsumi is a fangirl of the show.)

Fan Works
"Terry Goodkind: First of all, I don't write fantasy. I write stories that have important human themes. They have elements of romance, history, adventure, mystery and philosophy. Most fantasy is one-dimensional. It's either about magic or a world-building. I don't do either."
 * Not quite "fan fiction", the Sandstorm Reviews page dedicated to Terry Goodkind's Sword of Truth series has some very critical pastiches and parodies, including the short work that fits this trope, "The Sword of Truth (Non-fantasy Version)." As its header proclaims, this story was written in response to this statement by Goodkind in an interview:


 * After the second or third book, quite a bit of text is devoted to both world-building and long, drawn-out discussions on the mechanics of magic, so making no judgments regarding quality, there appears to be a bit of a disconnect between the author and his work, as this quote is from a press junket for the eighth in the series.

Films -- Live-Action

 * The Star Trek king of this was Star Trek IV: The Voyage Home, where Time Travel had our heroes attempting to blend in in 1980s San Francisco.
 * The setting of Superior Ultraman 8 Brothers was like this at first, before the monsters started invading.

Live-Action TV

 * Star Trek
 * Star Trek the Original Series gave us "A Piece of the Action", in which the crew visited a planet run like the Prohibition-era Mafia, complete with Tommy guns, pin-striped suits, and Model-A Fords. Many other planets resemble Earth's past to varying degrees.
 * They also actually visit the past of Earth in "City on the Edge of Forever" (The Thirties) and "Assignment: Earth" and "Tomorrow is Yesterday", both of which were set in the contemporary Sixties.
 * Star Trek the Next Generation, of course, had the holodeck. Data and LaForge were fond of acting out the parts of Sherlock Holmes and Dr. Watson, respectively. Of course, sometimes this caused problems, such as when Holmes's archnemesis, Professor Moriarty, took over the ship.
 * Star Trek Voyager has this in "Future's End", when the crew visit 1996. There's a clever subversion of the common trope of the Fan of the Past taking charge—Tom Paris is indeed an expert on the twentieth century, but on the mid twentieth century, and does The Great Politics Mess-Up when he mentions the Soviet Union to a local.
 * The Tenchi Muyo TV series had three episodes where the characters were dropped into other genres, including a High School drama and a Film Noir.
 * Being Human (UK): Various supernatural critters under one roof in contemporary times.
 * Stargate Universe is a borderline example. While the Stargate canon has many fantastic elements, it is set in modern-day earth with mostly normal humans. Universe, however, is set halfway across the universe in a You Can't Go Home Again scenario, but still uses a hallucination episode, "Cloverdale", to play the trope straight.

Myths & Relgion

 * Older Than Dirt: In Sumerian mythology, the goddess Inanna, known for her childish habit of losing her temper and causing widespread chaos and destruction, is married to the shepherd god Dumuzi. However, some ancient love lyrics and wedding songs feature Dumuzi as a regular shepherd who is courting Inanna, who appears as a temperamental young maiden.

Video Games

 * The ending of Chrono Cross has someone, apparently Kid, in our world shown realistically.

Web Comics

 * Interesting variation occurs in the webcomic No Need for Bushido (NNFB for short), which takes place in feudal Japan. A "subcomic" titled No Need for a Player's Guide shows the same characters—in the context of a contemporary, videogame-centric/wacky roommate webcomic. A Daimyo lord becomes a corporate executive, a rogue Ronin samurai becomes a FedEx man, and their habitual katana-duels to-the-death becomes videogame confrontations...
 * In the Walkyverse, Dumbing of Age is basically a Continuity Reboot that removes the sci-fi elements, moving the characters to a normal college setting.
 * Dawn of Time is about a Nubile Savage and her pet triceratops in a highly fantasy-themed prehistoric world, with some Time Travel to spice things up. One filler comic, though, transplants Dawn and Blue in a Buddy Cop Show.

Western Animation

 * Borderline example: The Disney series Tale Spin plunks several characters from The Jungle Book into a 1930s-era "Golden Age of Flying" environment. Baloo becomes a Genius Ditz pilot, Louie a barkeeper, Shere Khan a (relatively benign) corporate CEO. The actual plot of the film never enters into it.
 * In Aeon Flux, the ending of the more-than-usually Mind Screwing episode "Chronophasia" has Aeon apparently being recreated as an ordinary woman in our world.
 * The Powerpuff Girls gives us the episode "Oops, I Did It Again", in which Professor Utonium dreams of the girls reimagined as the "Run of the Mill Girls", who don't have superpowers or their distinctive Non-Standard Character Design. Towards the end, we also see that Utonium's career was also hit by mundanization—instead of working in a laboratory, he runs "Pizza Pie Laboratory", a take-out pizza joint. "Man, oh, man! What an exciting job!"