When I was in sixth grade, I had snuck a medical book down from my parents' shelf to find out about girls' parts. Lo and behold, when I went to lunch the following day at school, I said to my friend "Jeff! Jeff! Girls have THREE holes! THREE of 'em!" Some of the guys at the lunch table looked at each other and said "No way!" and waved me off. Some of the girls looked at me as if I were nuts.
A childhood belief about rude bits

others believed things like this
- I thought that the difference between girls and boys was that girls have teeth.
Anon - I used to believe all babies came out as girls and later on in life some of those girls turned into boys — Tom
- When I was little I thought girls had "man parts" as well, but it just took longer for them to grow.— person
- I used to believe that cats were the girls and dogs were the guys. Same with cows and horses.Anon
- In first grade a boy told me that he could see girls naked with his microscope lens. I beleived it for years.— Jeanette
- I used to think that girls' anuses were green. I remember thinking that as late as high school.— Jack