Canon, in terms of a fictional universe, is a body of material that is considered to be "genuine" or "official".
This is as opposed to non-canon material, which is a body of material considered to be a fictional offshoot of the canon universe or storyline. For example, one of the endings from Mega Man X5, X forgets the existence of Zero. This is considered non-canon as it doesn’t "really" happen.
To understand canon and continuity, the overall Mega Man series should be looked at as a set of stories written by many different people which "document" past "events." Although some stories are more reliable than others, they all are looked upon as part of the overall "history." It should also be remembered that all of these stories are simply that—stories. There are numerous errors that inevitably arise between the stories simply because different authors have their own ways of telling the story and may not have the time and resources to perfectly align the details.
The situation can be compared to Greek and Roman mythology, or the stories of King Arthur. The various Mega Man tales are a group of separate but linked stories, and are told by many different authors over a period of time.
Fanon is a term distinct from canon used to refer to facts or situations created by fans of a series. Such fiction is never regarded as canon.
The facts of some fanon are considered canon by a large number of fans, although it isn't. This often happens in plot-holes, but some also replace canonical facts. A major example is the Cataclysm event from the web comic Bob and George, where Zero killed most of the cast from the original Mega Man series when he was created, explaining why they didn't appear in the Mega Man X series.
Fanon can also take the form of personal beliefs held by individuals. In this case, an individual may create an expansive backstory, possibly a fan fiction, which he or she accepts as "true."
Fanon on MMKB
The Mega Man Knowledge Base does not accept any form of fanon whatsoever, because its main purpose is document official and licensed elements from the Mega Man series. Occasionally articles of very widespread fanon in the community are allowed, but these are tagged as being non-canonical and are not linked to canonical articles.
Addition of fanon material to existing articles as well as the creation of new fanon-based articles is considered vandalism. Personal fanon is only allowed on user pages, provided that it is clearly marked as fanon and is limited to a very small amount. For personal fanon, it is recommended the use of the Mega Man Fanon Wiki or other fan related site such as DeviantArt. If you known of a fanon related subject that is well known and can have an article in MMKB, you can request it here.
- Mega Man Fanon Wiki, a wiki devoted to fan-made Mega Man content.