Fandom of anything comes in two flavors; hardcore & casual.
Casual fans enjoy the show or game or book, but usually not enough to involve themselves in debates, fanart, fanfiction, & wikis. The ones that do work off limited memory of the subject.
Hardcore fans come in two flavors; purist & degenerate.
Purist fans insist that characters in fanfiction be completely in character & that the story has continuity nods. Degenerate fans change the personalities of characters to suit their needs, especially if the plot revolves around their Mary-Sue character.
Purist fans' OCs will not be romantically involved with canon characters & will be appropriate for the setting. Degenerate fans' OCs will look & feel very out-of-place with their surroundings, be deeply involved with canon characters, dress very differently than everyone else, & have a large number of special abilities & talents.
Purists purge any speculations that cannot be proved with solid evidence from Wiki pages. Degenerates create the speculations & often continue to stick with them even after the concepts have been steamrolled by new continuity. They also slash characters who canonically are not into eachother.
Purist fanart may or may not try to mimic the look of the original, but at least keeps it clean. Degenerate fanart includes humanizing animals, animalizing humans, breast inflation, porn, bestiality, pedophilia, weight gain, gratuitous nudity, & gender swapping.
1)The more unsavory fans of Adventure Time spend all their thoughts on potential pairings while the nerdier ones keep their eyes open for Mario & Zelda references.
2)Casual fans of Peanuts fancy Marcie & Peppermint Patty as lesbians, despite their established shared crush on Charlie Brown & the fact that they were only 8 years old. Is it wishful thinking or could they just not be assed to read the comics the TV series was based on?
3)Many believe that large adult male fanbase for Friendship is Magic to be creepy, but it is actually the 12-18 year old male fans who make the bulk of the fanart you can never unsee.