I was around 8 or 9. My mother was pregnant and I had questions! My Dad was doing the best he could explaining everything but he couldn't quite bring himself to tell how the sperm got from the man to the woman.
So, after MANY sessions going into all the anatomical stuff on each side and all the gestational stuff about the baby's progress, I finally got a little impatient and asked the crucial question.
"Dad, I understand all this stuff but HOW DOES THE SPERM GET FROM THE MAN TO THE WOMAN?"
My Dad wasn't generally a smoker but whenever we'd have one of these sessions, he was smoking. After this question he took a drag on that cigarette that consumed about half of it in one go. He said,"Well you know the man and the woman sleep in the same bed and sometimes they roll over on each other ACCIDENTALLY!" He totally ran for cover!
I still smile about this 50 years later.
A childhood belief about reproduction

others believed things like this
- I use to believe that the man peed in the woman to get her pregnant. Didn't know about sperm until sex ed. — das
- I used to believe that a baby's sex was determined by whether the sperm had a picture of a man or woman on it.— David E.
- My sister just recently realized that the lyric "more than a woman" wasn't 4 letter woman!— Anne
- I used to think that if a black woman or man and a white woman or man had a baby, it would be Asian.Anon
- I used to believe that when a woman was pregnant the baby could play monkey bars on her ribs.— Laura
- I used to believe that when a woman was pregnant, she fed the baby with a tiny spoon through her belly button.— Marie