In show business, a guest appearance is the participation of an outsider performer (such as a musician or actor) in an event such as a music record or concert, show, etc., when the performer does not belong to the regular cast, band or another performing group. In music, such an outside performer often referred to as a guest artist. In performance art, the terms guest role or guest star are also typical, the latter term explicitly indicating the guest appearance of a celebrity. The second is often also credited as a special guest star or special musical guest star by some production companies.
In pop music, guest appearances described with a feat. (abbr. as ft.) or with (abbr. as w/).
In a TV series, a guest star is an actor who appears in one or a few episodes (sometimes an entire story arc).
In radio and television shows, a guest star is a guest on the show who is a celebrity.