In media, a spin-off (or spinoff) is a radio program, television program, video game, film, or any narrative work, derived from one or more already existing works, that focuses, in particular, in more detail on one aspect of that original work (e.g. a particular topic, character, or event). A spin-off may be called a sidequel when it exists in the same chronological frame of time as its predecessor work. One of the earliest spin-offs of the modern media era, if not the first, happened in 1941 when the supporting character Throckmorton P. Gildersleeve from the old time radio comedy show Fibber McGee and Molly became the star of his own program The Great Gildersleeve (1941–1957).
In genre fiction, the term parallels the usage in television; it is usually meant to indicate a substantial change in narrative viewpoint and activity from that (previous) storyline based on the activities of the series' principal protagonist(s) and so is a shift to that action and overall narrative thread of some other protagonist(s), which now becomes the central or main thread (storyline) of the new sub-series. The new protagonist generally appears first as a minor or supporting character in the main story line within a given milieu, and it is very common for the previous protagonist to have a supporting or cameo role, at the least as a historical mention, in the new sub-series. Spin offs sometimes generate their own spin-offs, leaving the new show in its own series only vaguely connected to the original series.
Sometimes even where a show is not a spin-off from another, there will nevertheless be crossovers, where a character from one show makes an appearance on another. Sometimes crossovers are created in an attempt to provide closure to fans of another failed series. Sometimes show producers will re-introduce a character from an older series into a later one as a way of providing a connectivity of that particular producer's television "universe".