Secret identity

A secret identity is an element of fiction wherein a character develops a separate persona (usually adopting a pseudonym), while keeping their true identity hidden. The character also may wear a disguise (ranging from makeup or a mask, to a complete costume). A character may have several types of secret identities simultaneously (such as adopted names, pen names, undercover identities, and crime fighting codenames).

History
The use of secret identities dates back to the early 20th century with characters such as Sherlock Holmes, the Scarlet Pimpernel, the Lone Ranger, and Zorro. Starting in the 1930s, the concept of a crime-fighters, superheroes, and vigilantes (and their adversaries) adopting secret identities became more widespread in dime novels, pulp magazines, comic books, old-time radio dramas, movie serials, and other popular fiction. Such characters remain popular to this day.

Purpose
The artistic purpose of the secret identity on the part of the writers is that it allows the characters to have ordinary lives which can allow for human drama as well as create tension with the effort needed to preserve the secret. This can include challenges such as throwing off the suspicions of associates who suspect, and the need to quickly improvise means to get out of sight to change identities. And superhuman characters may benefit from an everyman aspect through having a secret identity, giving them a sympathetic link to their audience. For example, Captain Marvel's secret identity is a boy named Billy Batson - a deliberate attempt to play on the daydreams of a young readership.

Sometimes the distinction as to which persona is the "real one" may be blurred or confused, as has sometimes been the case with Clark Kent and Superman. For example, in the television series Lois & Clark: The New Adventures of Superman, after Lois Lane learns that Superman is Clark Kent, he discusses his dual identity with her. "Clark Kent is not a disguise. Clark is who I am, while Superman is what I do."

Some common motivations for a character to choose to have a secret identity include:
 * Allowing the character to live a "normal life" when not fighting crime.
 * Preventing the hero's enemies from seeking revenge on others the hero may care about.
 * Giving the hero an advantage in crime fighting (e.g. Batman or The Shadow striking fear into criminals).
 * Gaining timely information on incidents as they happen, often through their occupation or that of their associates (e.g. a reporter or a newscaster would likely be more informed about incidents that a hero might be able to help with).
 * Aliens, upon coming to Earth, may choose to set up one or more secret identities as a learning tool. By pretending to be humans, they can explore the different roles and lives that a regular human is expected to have in his/her life and using their deeper understanding of human condition to help others.