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Sidekick from WikiPedia:

A sidekick is a stock character, a close companion who assists a partner in a superior position. Don Quixote's Sancho Panza, Sherlock Holmes' Doctor Watson, Batman's companion Robin, and Xena's partner, Gabrielle are some well-known sidekicks in fiction.

The origin of the term comes from pickpocket slang of the late 19th and early 20th century. The "kick" is the front side pocket of a pair of trousers, and was found to be the pocket safest from theft. Thus the "side-kick" became an inseparable companion. As well the companion also helps the main character whenever they need it. A humorous folk origin for the term refers to their accomplishments being 'kicked to the side' or otherwise ignored in favor of the more charismatic lead hero.

In fiction, the term sidekick most commonly refers to assistants to heroes, usually in a crime-fighting capacity. The sidekick has the literary function of playing against the hero, often contrasting in skill, or performing functions not suited to the hero. By asking questions of the hero, or giving the hero someone to talk to, the sidekick provides an opportunity for the author to provide exposition.[citation needed]

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