Callback (comedy)
In comedy, a callback is a joke that refers to one previously told in the set. It is also known as an internal allusion, a literary device that helps give structure to the piece of writing. Callbacks are a subset of inside jokes which refer to something told in the set rather than to anything in general.
Television
In television, the term callback has come to mean a joke or line that refers to a previous episode. Particularly in earlier sitcoms—though even until the early 1990s—callbacks were rare and often frowned upon by networks, because they threaten to alienate a viewer who is new to the series, or who has missed episodes, particularly if the callback is tied to previous episodes.Seinfeld, a show built around stand-up comedy, regularly used callbacks in its scripts; its use of the strategy commonly kept the callbacks confined to events in the same episodes, having the effect of bringing the episode full-circle or creating an ironic twist ending. Another series, 30 Rock, employed callbacks to reference fictitious movies and television programs created within the show. Arrested [Development (TV series)|Arrested Development] became well known by fans for its regular use of callbacks throughout all of its episodes.
The line between a callback and simple continuity can be ambiguous. Repeatedly calling back to the same joke is a running gag.