my younger brother after his 1st day at school announced that he now knew the difference between boys and girls - boys have laces in their shoes and girls have buckles. still makes us chucklt to this day (28yrs later!!)
A childhood belief about appearance

others believed things like this
- I thought that the difference between girls and boys was that girls have teeth.
Anon - I used to believe that little boys grew up to be girls and little girls grew up to be boys. — Darin
- when I was a kid, I used to believe that only girls could be my friends and all other boys were my brothers.
— rajat - I used to believe that tigers were girls and lions were boys— Ruth
- I used to believe that all cats were girls and all dogs were boys.— jordan
- I used to think that all cats were girls and all dogs were boys. — trav