Alter ego

An alter ego (from Latin, "other I") is another self — a second personality within a person. It is also called leading a double life. The term "alter ego" was first used in the 19th century. It was inventory by psychologists in talking about dissociative identity disorder.

For example, in The Strange Case of Dr Jekyll and Mr Hyde, Mr. Hyde was Dr. Jekyll's evil alter ego (same person, different personalities).

In literature

The term is also used in popular fiction, like comic books, for the secret identity of a superhero, vigilante, or crimefighter. The character would do this so people won't know that he or she is fighting crime. Examples of characters using alter egos include:

Superman's alter ego is Clark Kent,
Bruce Wayne’s is Batman,
Peter Parker’s is Spider-Man

Music

Sometimes an artist uses an alter ego, like:

Ziggy Stardust was an alter ego from David Bowie
Marilyn Manson is the stage name of Brian Warner
Slim Shady is the alter ego from rapper Eminem