For a long time, I didn't know that guys got erections, so I thought that during sex, their penis would still be pointing down. Because of that, I couldn't envision how people could have sex. I'd seen sex scenes in movies where the guy would be on top of the gal, but I came to the conclusion that people just did that for a little while before having sex, and then they'd get into a new position where they'd lie with their heads at opposite ends of the bed, and would both move their legs apart really far and scoot close enough so that they guy could get inside her. I thought it was this huge physical feat.
A childhood belief about sex

others believed things like this
- when i was little i thought people with big heads or big noses had cancer...Anon
- i used to think water towers were houses for really tall people. I thought they had big heads to.— Alyssa
- I used to think a female daddy-long-legs was called a "mummy-long-legs".Anon
- when i was little i always asked my mom if my aunt had ant legs or people legs.— kelly
- I used to believe that gay guys had sex by sticking their penis in the other's penis.— Fanbrat
- I thought that psychological torture involved forcing people to watch really sad movies!— Elviessa