This isn't my belief, but a friend of mines. It was the funniest one I've heard. When she was young, she believed that if you poked your belly button, you would fly.
A childhood belief about belly buttons

others believed things like this
- I used to believe that if I poked my grandfather in the belly-button he would spit out quarters. — Justin
- i used to believe that if you poked yerr belly button yerr butt would fall off.— jordy
- when i was young i was told that if i played with or turned my belly button that my bum would fall off — lee hull
- I believed that if you pushed your belly button, your bum would fall off.— Wendy
- I used to think that if i touched my belly button it would unfold and my belly would be inside out forever. Anon
- One kid I know believed that because I wear glasses, it wouldn't hurt if he poked my eye.Anon