My head obsesses. I get songs stuck in my head so badly that I have to leave the room when "I'm On A Boat" comes on, and anyone who tries to troll me by singing "Party in the USA" gets warned and then ferociously tickled. (It's self-defense.) I don't like watching TV shows and have to limit movies because the scenes and plots continue to play in my head for days afterward, displacing the top idea in my mind.
The most interesting case of this is the Tetris effect. This where you do a repetitive activity so much that it takes over your subconscious, visually superimposing its patterns over your life. It's most noticeable when you're falling asleep. Tetris addicts would turn things they see into tetrominos, and their brains would be playing Tetris as they slept.
I have it bad. I've had the Tetris effect not only with all sorts of video games, but with things like coding, typing Dvorak, fixing grammar mistakes, responding to emails, hiking, tweaking CSS, and designing particle effects. Up until this week, though, it had only been visual, perhaps with some motor component.
It turns out I can get auditory Tetris effect, too. I had just spent the entire day strategizing about CodeCombat with George and Scott, talking startups with other Y Combinator companies, and listening to the YC partners dispense wisdom. As I was falling asleep, I heard a perfect Markov chain generator produce a conversation between Paul Graham, George, and Generic Startup Founder, complete with voices and appropriate verbal mannerisms, that went something like this: