When I was a kid, I really believed for a while that a little man lived in the refrigerator and turned the light on and off for you...why wouldn't I believe it? My parents told me that's how it was.
One fun thing about having kids yourself is you get to mess with their minds the way your parents messed with yours. This weekend, just before my wife took the whole crew out for the day, I pulled our 4 year old aside and convinced him that no matter what anyone says or asks him during the day, he should respond “I'm Batman.”
He did it. To my wife, and to the (surprised) guy running the bumper boats at the local fun park.