cameo

Originally, a cameo was a small piece of artwork, and in production refers to a bit part (usually a brief, non-speaking or walk-on role that is uncredited or unbilled) or special screen appearance by a famous actor, director, or prominent person who would ordinarily not take such a small part. A cameo is in contrast to a "bit part." Also refers to a type of camera shot in which the subject is filmed against a black or neutral background. See "directors' cameos."