My step-dad used to tell my little sister that if you un-screwed your belly button that your arms and legs would fall off.
A childhood belief about belly buttons

others believed things like this
- 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
- someone could unscrew my belly button, and if they did, my head would fall offAnon
- 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