Fandom can be miraculous. Fans bring so much creativity and love to science fiction and fantasy universes, and along the way they work an amazing transformation. And sometimes it feels like the stories the fans create are actually cooler than the works they're based on.
So what science fiction or fantasy universe do you prefer the "fanon" or the fan fiction to the actual thing? For me, it's probably Star Trek: Voyager. I've read some Voyager fanfic that blew my mind, or at least made me giggle loudly.