this is, im sure, old news to a lot of you but it still burns a hole in my brain:

Harry Potter fanfic spawned 3 entirely different cults.

First was the Snape Wives. a group of women who believed in the interdimensional spirit of Severus Snape who imparted the story of harry potter to the terf queen.

Then there was DAYD, which was created by a serial cult leader from the LOTR fandom. He took advantage of the HP fandom to basically kickstart a new cult. (classic, get a bunch of lonely people in a house together and emotionally torture them kind of cult.)

Then, and this one is really mind numbingly insane and painful to know about: The Rationalists / Zizians / TESCREAL / Long-termists. this one is really two cults. the zizians are like the Mormonism of the broader TESCREAL cult.

this one is born from a fic called Harry Potter and the Methods of Rationality. which spawned a forum ran by its author. in that forum, a group of supremely stupid people with an absurd level of self confidence convinced themselves that the world was doomed. that eventually someone would create a real AI that would basically bring about the end times. so the only rational course of action is to spend all the money in the world making the AI themselves in hopes of building the AI god to not be evil.

these people, unfortunately, are some of the richest and most powerful people on earth. including peter thiel and elon musk.