Lemon Shipping Rules et al.
Fapnon is, duh, a subtrope of Fanon. Lemon/Rule34/Hentai/whatever fanon has, IMHO, very specific tropes. As a random example, any lemon (I know of) with Vampirella and Pantha declares them to be a lesbian pair even although canon shoots this down. (There are more fanon rules than just who gets shipped - just want to start the discussion. Feel free to extend and elaborate, it's just a raw idea.)