To listen to music before going out of the house, and having the last song you hear before leaving stick in your head all through your journey, and beyond. Is usually accompanied by subconscious humming. This syndrome is particularly dangerous when the song happens to be the most pathetic, crappy, albeit catchy song ever.
I stupidly tuned into Crap FM before going to work, and had 'Barbie Girl' playing over and over and over in my head all through the bus ride. That's why I cut my wrists Doc.