When I went to see the Lego movie, I went with a friend who had already seen it - he played the soundtrack the whole way there, so the song was stuck in my head before I had even seen the movie!

Right now I've got Sara Bareilles' "Brave." Similar to Perry's "Roar," but just a bit less cheesy. A bit. I hear this stuff on the radio and then it's in my head for the rest of the day.