What I have learned about Fandoms purely through Tumblr in one sentence (spoilers maybe?) 

• Supernatural: There are two brothers who are having sex with each other and an angel, and one of them is a moose.
• Doctor Who: An English gentleman who is upset about being human will come in a large blue police box at any point in time to make the most ridiculous faces at you.
• Sherlock: An otter and a hedgehog solve crimes in a division not covered by any man.
• Mass Effect: A woman has sex with a lot of aliens, while one man's butt saves the universe.
• Dragon Age: A man wearing feathers and obsessed with kittens has sex with anyone who has a penis, and a few chicks, too.
• Game of Thrones: Everyone dies, but only if they just promised to tell someone something important when they get back.
• Avengers: There is a superhero orgy and everyone is invited but the Hulk and Black Widow.
• Skyrim: FUS RO DAH
• Homestuck: Something about yaoi trolls with Lisa Frank colors making out on stairs. And they all have sea slug penises.
• The Hunger Games: Some people who play real life Sims with some kids. One of them loves bread.