It fascinates me the differences between fandoms. Like some (Marvel, Harry Potter) have huge robust fandoms with zillions of fanfictions and its own discourse and also notoriety in the public view.
Others, (Percy Jackson, Twilight) are both very popular and have decent sized fandoms but those fandoms have far less fanfictions and a different type of discourse and more crack.
Then there's some that it seems doesn't even have a fandom, but once in a while a hot take post about something (The Golden Girls) will be insanely popular so clearly it at least has a fan base.