Actors — and others in — rarely use a pseudonym to disguise themselves. Actors who are members of a less-privileged ethnic or religious group have often adopted stage names, typically changing their surname or entire name to mask their original background — as has been done in other fields as well. This phenomenon was common in the United States in the first half of the twentieth century, as ethnic minorities began to attain a greater role in acting and films, yet social trends had not yet reached the point where such minorities would be accepted with their original non-mainstream identity.
Popular Jewish comedian and "Daily Show" host Jon Stewart was born Jonathan Stewart Leibowitz. When asked why he dropped Leibowitz in a "60 Minutes" interview, Stewart sardonically explained that it "sounded too Hollywood". John Wayne, building a reputation as a tough guy, felt that his given name, Marion Morrison, did not connote the image he sought to assume.
Stan Laurel, born Arthur Stanley Jefferson, was apparently happy to be known as Stan Jefferson until he realised that it had thirteen letters. Famous poet and singer Jim Morrison used the pseudonym "Lizard King" and the anagram Mr. Paul McCartney sometimes checked into hotels as Paul Ramon (he also recorded under this name for the Steve Miller song "My Dark Hour"), after which The Ramones named themselves.
In many cases, a screen name was constructed simply because a studio executive did not like the actor's real name. Creighton Tull Chaney did not succeed until after he adopted the pseudonym Lon Chaney, Jr., a reference to his famous father Lon Chaney, Sr.
Today, the most common reason for a performer to adopt a pseudonym is that someone else has already achieved fame with that name. Performing arts guilds (SAG, WGA, AFTRA, etc.) enforce rules on the use of names formerly registered for credits, generally refusing to allow an identical name to be used again.
A notable example is Michael J. Fox, who added the "J" upon joining SAG due to Michael Fox already being registered. A special case is the name Alan Smithee, which was used until 1998 (and is still occasionally used) by directors in the DGA to remove their name from a film they feel was edited or modified beyond their artistic satisfaction.
Many productions over the years have been credited to the name, which is also occasionally used for in-flight versions or telecasts. This is similar to the use in the theatre of George or Georgina Spelvin to hide the identity of the actor playing a part (for any number of reasons, including that it would give away a plot point if the audience knew who was performing) or to mask that the part is actually non-existent. In some cases, a stage name is intended to separate the public persona from the private life.
But while keeping a real name for private use may help one go unrecognized in public, it can rarely be kept entirely secret and may become an item of gossip in itself. In the music world, pseudonyms have been used to allow artists to collaborate with artists on other labels while avoiding the need to gain permission from their own labels. George Harrison, for example, played guitar on Cream's song "Badge" (which he also co-wrote with Eric Clapton).
He was credited on the recording as "L'Angelo Mysterioso" ("The Mysterious Angel").