Fan theories are fun, but what makes a good fan theory? Secret crossovers between unlikely characters are fun, like how we learned Clueless and Frasier are in the same universe. Genre-bending backstory, like I Love Lucy's mafia prequel, those are interesting and wacky to contemplate. Elden Ring trolling torrent pirates? That gives us all a warm chuckle.
Beyond fun, though, a good fan theory expands the audience's engagement with the art. The documentary Room 237, for instance, is two hours of people letting their minds run wild over The Shining, some ideas baffling and some chin-scratching, until finally Bill Blakemore says “The Shining is about genocide of Indigenous peoples in America” and the whole internet goes “whoa, he's right.” Conversely, some fan theories deliberately miss the point of an entire TV series, like this one about BoJack Horseman dying but somehow not becoming glue? At least the very least, fan theories are great discussion topics, so the following should keep you and your friends talking for decades: