Back to the Future slash
From Fan History Wiki
The slash subset of Back to the Future fandom began officially on April, 19 2003 when DrWorm posted a short piece of Marty/George fanfic to FanFiction.net. While the fic itself contained only a brief kiss between two male characters, it drew quite a bit of ire not only for the perceived homoeroticism but also for the pairing's incestuous implications. Nonetheless, writers such as Nightspore and Kleenexwoman soon followed with their own fics, and the three continue to make up the core of Back to the Future slash fans.
Before the first intentional slash fic was posted, some Back to the Future fans reacted to Flaming Trails' fic, Ich Liebe Dich, as if it was a Doc/Marty piece. Flaming Trails has since made it clear that she does not associate with those who write slash and did not intend for her story to be read in such a way.
Fandom hostility toward the concept of slash was not limited to FanFiction.net or to the larger names in the fandom. The BttF.com messageboard, the largest and most influential gathering for fans of the movie, deleted posts and banned users having anything to do with slash  before removing their section for fan-created work entirely.
In 2006, the comedy troupe Chocolate Cake City released Brokeback to the Future, a creative edit of footage from Back to the Future that satirized the much-talked-about trailers for the film Brokeback Mountain and placed Doc and Marty in the starring roles. The video was circulated widely, and enjoyed by many as the parody that it was. Very little complaint came from within the quiet fandom itself , however BttF.com chose to remove posts linking to the video from the messageboard .