In works of fiction

Fiction

Fiction is the form of any narrative or informative work that deals, in part or in whole, with information or events that are not factual, but rather, imaginary—that is, invented by the author. Although fiction describes a major branch of literary work, it may also refer to theatrical,...

, fanon is a customary and unofficial canon

Canon (fiction)

In the context of a work of fiction, the term canon denotes the material accepted as "official" in a fictional universe's fan base. It is often contrasted with, or used as the basis for, works of fan fiction, which are not considered canonical...

 established in a spontaneous manner by the community of fan

Fan (person)

A Fan, sometimes also called aficionado or supporter, is a person with a liking and enthusiasm for something, such as a band or a sports team. Fans of a particular thing or person constitute its fanbase or fandom...

s at large, for example fan club

Fan club

A fan club is a group that is dedicated to a well-known person, group, idea or sometimes even an inanimate object . Most fan clubs are run by fans who devote considerable time and resources to supporting them. There are also "official" fan clubs that are run by someone associated with the person...

s, whenever the official canon is not clear on some points of its narrative.

Fanon is a common feature in large franchise

Franchise

Franchise generally means a right or privilege. It may refer to:*Suffrage, the civil right to vote*Franchising, a business method that involves licensing of trademarks and methods of doing business, such as:...

s and fictional universe

Fictional universe

A fictional universe is a self-consistent fictional setting with elements that differ from the real world. It may also be called an imagined, constructed or fictional realm ....

s where there are many canon and non-canon works, as in the Star Trek universe. Sometimes, fanon comes from the acceptance of non-canonical explanations provided in expanded universe

Expanded Universe

The term Expanded Universe is generally used to denote the 'extension' of a media franchise with other media...

published works.