guest star

guest actor, actor that is not a part of the regular team of actors

A guest star, relating to a television series, is an actor who appears on one or several episodes (playing a character or themselves). Sometimes the definition can become blurry, as some guest stars have appeared on entire seasons of shows (eg. Jonathan Harris on Lost in Space), while some have become integral to the show (eg. Heather Locklear on Melrose Place). Guest stars are sometimes well-known personages prior to becoming guest stars, with their popularity being used to draw attention to the show they're guest starring on.
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