When my (much) younger sister was six or so, I made some sort of comment to her about food turning into poo. She looked confused, and I said "When you eat food, it goes though your body and comes out as poo. Didn't you know that?"
She looked confused.
"Where did you think poo came from?"
She admitted that she thought a machine came into her room at night and "put poo up my bum for the next day."
I have >no< idea where she got that idea, but you can bet I'm going to mention it at her wedding reception.
A childhood belief about weeing and pooing

others believed things like this
- Good looked exactly like George Washington.
I have no idea where I got this.— Leen - I thought when you got food poisoning it might someone had put poison in your food— Bootlebat
- I use to believe that salt would cool food down while pepper would heat your foodAnon
- I used to believe when ordering Chinese food the food and delivery man came from China— Dave
- I used to beleive, that if you swallowed a seed the food would grow in your body.Anon
- i thought salt made food cold, since pepper made it *hot* — cattiva