This is when a show that normally does California Doubling stops doing that for an episode or two, by moving the plot to the same location where the show is usually filmed.
Let's say that Generic Detective Show is filmed in Los Angeles, but it's set in New York. They find an actor who can do a Brooklyn accent, throw in some establishing shots of lower Manhattan, and with some clever editing it's pretty convincing as a Big Applesauce series. But then after two or three seasons, one episode involves Detectives Alice and Bob following a lead to Los Angeles. Suddenly, there's Scenery Porn. The show takes place outside more. The establishing shots actually have the characters in them.
In short, a Filming Location Cameo gives an episode the novelty and excitement of shooting on-location in a different city...but since it's not actually a different city, it's generally cheaper. By its nature, the technique is almost entirely exclusive to live-action TV, although film examples are theoretically possible.
May be used for a Vacation Episode.
To reiterate: this is the show being temporarily set where it is already filmed, not just filmed where it is set. There must be a clear pattern of California Doubling that is then broken by the plot, without changing the filming location. If the cast and crew have to travel anywhere out of the ordinary to shoot the episode, it's not this.
- Alphas (set in New York City, filmed in Toronto) has an episode where the epilogue takes place in Toronto.
- Bones (set in Washington D.C., filmed in L.A.) has a few:
- "The Woman at the Airport": the characters travel to L.A. to investigate a murder.
- "The Suit on the Set": the characters return to L.A. to consult on a film, where they discover a murder.
- "The 200th in the 10th": an Elseworld episode with the characters living in 1950s L.A.
- Castle, usually set in New York but filmed in L.A., has "To Love and Die in L.A.", where Beckett follows the trail of the man who killed her mentor to Los Angeles.
- The Dead Zone (set in Maine, filmed in Vancouver): one episode Johnny visits a man living in Vancouver.
- The revived series of Doctor Who is filmed in Cardiff, which consequently has stood in for London, New York and other exotic locations. The first-season episode "Boom Town" is set in Cardiff, and features the TARDIS parked in front of a recognizable Cardiff landmark with another in the background.
- Lost (set on a mysterious island, filmed in Hawai'i): When the Oceanic Six are rescued, they land in Hawai'i.
- The later seasons of Power Rangers are filmed in New Zealand, but are set in towns and cities in America. However, there was a story arc of Power Rangers Dino Charge where the rangers visit New Zealand to hunt for a new Zord.
- Psych is filmed in Vancouver, but normally set in Santa Barbara. However, there are two episodes where the characters take a trip to Vancouver: the Vacation Episode "Extradition: British Columbia", and its sequel "Extradition II: The Actual Extradition Part".
- Rizzoli & Isles is set in Boston, but filmed in Los Angeles. In the season 6 episode "Fake It 'Til You Make It", the titular characters discover that their latest murder case might be tied to a similar one in Los Angeles, so they fly out to take a look.
- Star Trek: Voyager: a temporal version in "Future's End" where the crew happen to be in Los Angeles and in 1996.
- Supernatural: in one episode they magically become two TV actors named Jensen Ackles and Jared Padalecki filming a show called Supernatural, and the bulk of the episode takes place in the TV studio where the show is actually shot.
- Time Trax being filmed in Australia has a few episodes set there, though largely set in U.S.
- Likewise Farscape. This is handwaved as the Farscape module being tested in Australia. Ironically it turns out the protagonist is not in Australia or anywhere else on Earth.
- The X-Files:
- Mulder and Scully's work takes them to Vancouver in "The End", which was aptly enough the last episode filmed in that city.
- After they moved shooting to LA, the episode "Hollywood, A.D." where somebody writes a movie Very Loosely Based on their work partially takes place in LA.
- Due South is set in Chicago but filmed in Toronto. In one episode Fraser and Ray go to Toronto - that single episode was filmed in Chicago.
- Leverage stretched this from "cameo" to something much longer. For much of its run, the series was set in Boston but actually filmed in Portland. In the final season, the main characters move their base to Portland, and the show suddenly started showing the local landmarks it had had to hide up until then.