My mom used to tell us when we were little that if we put our fingers in our belly button it would unscrew our arms and legs and they would fall off. I think we were about 12 when we finally decided that it wouldn't really happen.
A childhood belief about belly buttons

others believed things like this
- someone could unscrew my belly button, and if they did, my head would fall offAnon
- If you undo your belly-button with a screwdriver, your legs will fall off.— Toby
- When I was a kid my dad told me that if you unscrewed your belly button your bum would fall off.— Ann
- i was told that if you fiddled with your belly-button too much, my bum would fall off.Anon
- I believed that if you pushed your belly button, your bum would fall off.— Wendy
- I used to believe that if your belly button came undone your skin would fall off! Anon