So what does Urban Dictionary have to say about fandoms?
Doctor Who: The show that breaks you down, tosses you around, punches you in the feels, and supports and smashes your OTP
Sherlock: Its a modern take on the classic Sherlock Holmes stories. Also the best tv series you will EVER watch; made by the evil, amazing Mark Gatiss, Jim Moffat and Stephen Thompson. May I suggest trying to get yourself emotionaly prepared for the most intese feels you will ever have; but to be honest, it won't help.
Supernatural: A show on The WB starring hotties Jensen Ackles and Jared Padalecki as Dean and Sam Winchester, respectively. The duo fights monsters, demons and reapers as they search for their father and the creature that killed their mother 22 years ago.
Homestuck: It is notable as a webcomic for it's speed of update (At least two pages a day if Hussie is not animating a flash), It's flash pages complete with a decent soundtrack, Its endearing characters and the occasional absolute horror it can inspire.
Merlin: [Not Defined]
Harry Potter: If you have to urbandictionary this you're obviously a muggle.
Twilight: The book designed for teenage girls to get off to and teenage boys to secretly read under their covers with a flashlight each night trying to feed off of what Edward does in hopes of getting a few pointers in winning girls over. Everyone will have negative things to say about this but all I can say is, congrats Stephanie Meyer; you sure won over the minds of a billion hormonal teenage girls by talking about Edward's chizzled jawline for 4 books straight
LOTR: Three movies about a bunch of midgets walking to a volcano
Avatar TLA: The story of a kid who can bend air without hair.
Starkid: a group of people graduated from University of Michigan that write and perform musicals (mostly known for their fan-made Harry Potter musical: A Very Potter Musical)...They also all have nice butts