There's an old joke in my family that's been passed down for generations as a means of curbing pyromaniacal behavior. "If you play with fire (or a campfire [ie: throw weeds, leafs, fireworks, etc. in it]), then you'll wet the bed!" I believed this well into the 7th grade. It has recently been taught to the children of family friends, who rarely play with fire.
A childhood belief about weeing and pooing

others believed things like this
- i always thought it was Grape Balls of Fire instead of Great Balls of Fire— Courtney
- i used 2 think if u lied your pants would catch on fire cus of the sayin "lier lier pants on fire!"— nell
- I used to be terrified of fire-flys because I believed they would burn if they landed on me.— kevin
- my sister told me that bunkers on golf courses were for children to play in while their dads played golf.— Julie
- I was about 6 and thought my family invented the fart because I never heard anyone outside my family do it.— Bob
- When I was little I used to believe that if I played with fire, then I would wet the bed. — Danielle