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Examples of type 1 (characters involved in production)
The numerous parody serials put on — in every sense of the word — by radio satirists Bob & Ray, as part of their own radio programs. The duo went so far as to invent fictional writers, producers, announcers and cast members, all of whom would frequently argue amongst themselves in the course of an episode.
The radio series of The Mighty Boosh briefly features Colobos the Crab, a televesion program of which Vince appears to be a fan, although the content is left both vauge and suitably absurd.
Examples of type 3 (SWAS is plot point)
Played with by Evermore's song "Hey Boys and Girls", from the concept album Truth of the World: Welcome to the Show. As part of the album's plot, it's a broadcast by the eponymous radio station. But it was also released as a single, and when it's played alone on the radio, with the opening line "We're interrupting transmission... welcome to the show" - it looks like Truth of the World just took over your radio station. The show-within-a-show has broken out of The Show and is now running the show...