My brother told me the bare fact about reproduction (penetration) and it sounded so complicated that I figured the man and woman had to go to a doctor to get the thing done. They would stand facing each other and then the doctor would carefully guide the man's penis into the woman. There would be a very professional medical quality to all of this and great embarrassment for the man and woman...but it was the only way.
A childhood belief about reproduction

others believed things like this
I used to believe a man and a woman needed a doctor to put their parts together when they did it.— Phil- My sister just recently realized that the lyric "more than a woman" wasn't 4 letter woman!— Anne
- I thought the line in the song "more than a woman" was "four-legged woman".— boo
- 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 once a man and a woman lay naked caressing each other, the woman would be pregant— oiman
- I used to think that the song "Evil Woman" was "Medieval Woman". Anon