Badfics exist as the poison of the Internets, written by bewildered fans in hopes that others will marvel over their miniscule attempts to create an original scene from their favorite annie may or some shit. Although many fanfics predictably fail because of their poor writing and mediocrity, one can actually find a good fanfic but only in rare instances.
Boring Historical Details
At least 100 years ago, numerous fanfics have been written featuring anything from yaoi to furries to...aw, hell...yaoi and furries. Fans who show a great interest in their favorite shows can go as far as to combine two series or more for a fanfic, thus giving birth to either an abomination of no redeeming quality or something that is actually worthy of lulz.