A sidekick is a stock character, a close companion who assists a partner in a superior position. Sancho Panza in Don Quixote, Doctor Watson in Sherlock Holmes and Batman's companion Robin are some well-known sidekicks.
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.
Those functions may include comic relief. The comedy relief sidekick was a common feature in westerns, where Fuzzy Knight, Al "Fuzzy" St. John, Smiley Burnette and Andy Devine had longer careers than some of the heroic singing cowboys for whom they took pratfalls. In science fiction a subtype of sidekick has been established—namely, the alien sidekick.
It may also be argued that the comedy sidekick's apparent stupidity makes a non-intellectual hero look intelligent. An openly flamboyant effeminate sidekick may make a non imposing hero look more masculine. A strong, silent and modest hero may have his fighting qualities revealed to the other characters and the audience by a talkative sidekick.
Hero Sidekicks not only provide comic relief but can occasionally be brave or resourceful at times and rescue the hero from some dire fate: such as Streaky the Supercat of Krypto the Superdog or Festus Haggen of Gunsmoke's Matt Dillon or even Paul Reiser to Helen Hunt from Mad About You.
Sidekicks also frequently serve as an emotional connection, especially when the hero is depicted as detached and distant, traits which would normally generate difficulty in making the hero likable. The sidekick is often the confidant who knows the main character better than anyone else and gives a convincing reason to like the hero. Although Sherlock Holmes was admittedly a difficult man to know, the friendship of Dr. Watson convinces the reader that Holmes is a good person.
While many sidekicks are used for comic relief, there are other sidekicks who are less outrageous than the heroes they pledge themselves to, and comedy derived from the hero can often be amplified by the presence or reaction of the sidekick. Examples include Porky Pig, who was more sensible and calmer than Daffy Duck in later short films; Sancho Panza is more rational than his master, Don Quixote.
While it is usually the reverse, it is not unheard of for a sidekick to be physically more conventionally attractive, charismatic, or physically capable than the character who is intended to be the hero. This is most typically encountered when the hero's appeal is supposed to be intellect instead of sex appeal or physical prowess. Such characters are often middle aged or older and tend towards eccentricity; fictional sleuths and scientists for example. Such sidekicks are rarely encountered in fiction because the hero runs the risk of being upstaged by them. However, examples of successful such pairings include Inspector Morse and his sidekick DS Robbie Lewis, Nero Wolfe and his sidekick Archie Goodwin or Doctor Who's Second Doctor and his sidekick Jamie McCrimmon.
Conversations with the sidekick reveal plot narrative devices to the audience in the form of conversation, thus the sidekick can have the same role as a Greek chorus.
A villain's supporters are normally called henchmen, minions, or lackeys, not sidekicks. While this is partially a convention in terminology, it also reflects that few villains are capable of bonds of friendship and loyalty, which are normal in the relationship between a hero and sidekick.