Fanon

Fanon has several definitions, and is a term that applies to almost every media-based or Internet fandom. per the TV Tropes Wiki, fanon is "the set of assumptions based on that material which, while they generally seem to be the 'obvious' or 'only' interpretation of canonical fact, are not actually part of the canon. Occasionally, the explanation seems good enough to just be 'common sense.'" In other words, fanon is what the fans think fills in the gaps in the original show.

In Daria fandom, fanon might mean:

1. Anything in Daria that is not strictly canon, but does not contradict canon and is therefore widely accepted by most fans. Many (but not all) fans have concluded that Highland was located in Texas and that the Morgendorffers moved out of Texas to Lawndale, located in Some Other State But Not Texas. Many fans have given Daria the middle name "Louise" or "Anne." None of these conventions explicitly defies canon, and could therefore be considered "fanon."

2. Any fan-created character or item popular enough to be used by other fans. In Daria fandom, examples include Kyle Armalin, Lynn Cullen, and Jim Vitale. In essence, these characters could be considered part of a Daria Expanded Universe, as long-time fanfiction readers know the characters so well that they can joke about their foibles and personality characteristics without feeling the need to explain to newcomers who those characters are.

The term "fanon" originally consisted only of the first definition, but has expanded to include the second definition above.