When I was 10 years old my labrador retriever impregnated my chihuahua. From that moment on I thought men's penises could get stuck inside women's vaginas.
p.s. they eventually unstuck and the puppies were adorable.
A childhood belief about sex

others believed things like this
- Women were impregnated by eating a lot of cheese— George
- Until about age 11 i thought that "Hush Puppies" the shoes were made from real puppies!— Laura
- I used to think that women had penises, but that they were just hairier than mens'.— Ameeratron
- I used to believe (about 9) that a penis was a sausage that men stuck in their crutch area to attract women.— Feebs.
- When I was a kid I thought girls peed out of there vaginas...woops!— Greg
- I used to believe that If I stuck my finger really far inside of my belly button I could touch my insides.Anon