I used to believe that the Daddy used to wee inside the Mummy to make a baby and the more wee-wee he did inside her meant you were taller when you growed up.
A childhood belief about reproduction

others believed things like this
- When I was first told about intercourse, I didn't believe it. How could peeing inside a girl make a baby?— Art
- I used to beleive before mummy and daddy "did it" they had to get "spunk cream" from the chemist. Anon
- that when I growed up I would be a footballer but that was obviously rubbish as I can't play for toffee— Darren
- I used to think cut and paste meant there were scissors and glue inside the computer!Anon
- when i was little i used to think that drinking soup would make me taller — gella pas doue
- I used to believe that inside each volcano there was a guy who'd press a button to make it erupt.— Jim, UK