I used to believe that if a girl thought that you were a boy and you weren't, you would automatically become a boy, because 'girls knew everything'.
A childhood belief about appearance

others believed things like this
- I used to think it was true that only ugly girls poop and I thought I was an ugly girl because I poopedAnon
- When I was a little girl, I believed that all cats were girls and all dogs were boys. :)— Mary Ellen
- I thought that the difference between girls and boys was that girls have teeth.
Anon - I used to believe that grilled cheese was called 'girl cheese,' and only girls could eat it.— Paige
- I once knew a girl who used to believe that the sun was actaully a really bright gold fish very high up.— meow
- When I was little I used to think that as soon as you were married the woman automatically got pregnant.Anon