fanon n. the body of widely accepted fan-created embellishments of a fictional universe, storyline, or character. Editorial Note: Thanks to Ruth Czirr for suggesting fanon as an entry. Etymological Note: fan + ca(n)on. The person quoted in the first 1998 citation has not been verified as the creator of the term fanon. (source: Double-Tongued Dictionary)
Further reading
Enthusiastic book recommendations! Martha’s savoring the biography of Alexander von Humboldt, the 19th-century explorer, polymath, and naturalist who revolutionized our understanding of nature and predicted the effects of human activity on...
We use the term Milky Way for that glowing arc across the sky. But how people picture it varies from culture to culture. In Sweden, that starry band goes by a name that means “Winter Street,” and in Hawaii, a term for the Milky Way...
I find it highly appropriate that four of the five examples used are from four of the largest ‘fanon’ universes: Star Trek, The Sentinel, Harry Potter, and Stargate.