When I was a kid I heard, "His penis reached his belly button". I thought it meant that there was this ridge above the actual penis that extended up to the belly button. Sort of like a Klingon brow ridge. Obviously, I am a girl.
A childhood belief about rude bits

others believed things like this
- I used to think that oral sex was when the guy put his penis in the girl's belly buttonAnon
- I used to think that if i touched my belly button it would unfold and my belly would be inside out forever. Anon
- when I was a kid I thought that babies come out of a belly-button.— Ana
- My mom says that when she was growing up, she thought that her belly button was where her skin came together.— Dana
- when i was younger i thought that babies could see out of the mummies belly button— strawberry
- i used to believe when you had a baby it would come out of the belly button— cortni