Midquel

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In addition to prequel and sequel one might coin the midquel for an episode that happens not before (because the group hadn't gotten together yet) nor after (because, uh, spoilers?) but during the events depicted elsewhere. The Cowboy Bebop movie comes to mind as a midquel. These are probably rare? Possibly midquels could be a subset of lost episodes that are located within the timeline not before or after it. This probably works better if one has a storyline or plan to fit new things into e.g. the Star Wars universe(s), or can fudge events with stardates and faster than light photonic gradient flux… look, squirrel!