Guest star
From Freepedia
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, 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.
The term guest star can also refer to other media as well. For example, in fiction, when characters from one media appear in another. Comic books, in particular, are known for having superheroes guest in another hero's book, though there are other examples.
