There was this really REALLY horrible pony story tumblr account called "Little Miss Rarity." Think "Cupcakes" Pinkie Pie, but Rarity. She err, kidnaps and kills Pinkie Pie, embalms her, and turns her into a doll. The official category is called Grimdark, and its awful. I just looked it up and it appears the comic has been banned and all accounts associated with it have been banned as well on Tumblr. I'm not sure that its banning was necessary, because I think it should have stood as an example of a fandom taken too far.