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 other performing group. In music, such an outside performer is often referred to as a guest artist. In performance art, the terms guest role or guest star are also common, the latter term specifically indicating the guest appearance of a celebrity. The latter is often also credited as "special guest star" or "special musical guest star" by some production companies. A guest character is a character being portrayed within a fictional entertainment setting who's only involved as part of the plot once or a few times at most. A guest character has less appearances than main characters, supporting characters, and recurring characters.
In pop music, guest appearances are often described with the words featuring, with, or and. It is abbreviated in credit lists as Feat., Ft., f/, f.
In television series, a guest star is an actor who appears in one or a few episodes. In radio and television shows, a guest star is a guest of the show who is a celebrity.
Classical performance arts 
Guest appearances have been known in theatre, ballet, and classical music for centuries, with guests both from the home country and from abroad. The advent of air transport has made this practice much more practical and global.
In classical music, guest orchestra conductors are a common practice.
Guest artists should not be confused with touring groups, troupes, orchestra, or even individual artists, although the distinction may be blurred. In the case of touring, their act is independent in itself, while the guest takes part in the act of the resident staff.
The duration of involvement of a guest artist may vary, from separate short-term acts with fees per concert to fixed temporary contracts for several seasons.
Pop music 
In the early days of the pop music industry the bands were relatively stable units, and while guests were not uncommon, they were seldom given credits on album covers. For example, Eric Clapton was not credited in print for his guitar in the release of While My Guitar Gently Weeps of the Beatles. Still the term "featuring" was used as early as in the July 1954 UK Singles Chart by "The Four Aces featuring Al Alberts" with "Three Coins In The Fountain" at 5th place. Gradually guest appearances have become a fully credited staple of music industry. The custom of guest appearance has become especially prominent in rap music, and this influenced rock musicians as well.
To have a guest star on a record, the production coordinator must obtain permission from the record label of the guest and make sure that proper credits are delivered to the host record label to be printed on the album cover, often in the form "Artist name, courtesy of Record Label name." The permission is not always granted or negotiations may take a long time.
Reasons for guest appearances 
A common reason for guest appearances is to draw attention to an act by including a celebrity into it. And vice versa, in the fashion-driven environment of show industry older stars keep themselves in the limelight by associating themselves with emerging stars.
In rap, mutual and multiple guest starring was recognized as a way to diversify the performance.
In theatre and ballet, guest appearances diversify actor's repertory and experience under different choreographers, and give more acting opportunities. Even for established stars prestigious overseas engagements increase their home status. Conversely, a guest star benefits the receiving troupe, bringing new inspiration and technique. Audience would welcome diversity, and theatrical business benefits as well: theatre connoisseurs will come to see the same piece with a new star.
Commercialization of guests policy may also have negative consequences. Local theatres may limit the growth opportunities for their performers in favor of guests. Sometimes rehearsal times are inadequate to fully integrate the home and guest styles. Touring increases physical load on an actor. It is also associated with multiple stress factors: from jet lags to close calls due to unanticipated travel delays.
See also 
- "The Dance Encyclopedia" by Anatole Chujoy, Phyllis Winifred Manchester, 1967, Simon and Schuster, p. 434, article "Guest Artist"
- "The Ballet Star as Guest Artist", Barry Laine, The New York Times, January 7, 2008
- "UK Top 40 Hit Database". Retrieved 2006-07-25.
- Voices find gilt by association, Mark Edwards, November 22, 2007, The Australian
- Bobby Borg (2003) "The Musician's Handbook: A Practical Guide to Understanding the Music Business", ISBN 0-8230-8357-8
- Jump the Shark.com. "Jump the Shark - Special Guest Star". Retrieved 2008-10-21.