Around the age of 8, a friend told me that sex involved "mars bar parties". For a couple of years I was confused about sex, because I knew Mars Bars had to be involved somehow, but I couldn't figure out how they needed to be used!
A childhood belief about sex

others believed things like this
- That "guerilla warfare" involved real Gorillas.— Geoffrey
- I thought that smoking pot involved an actual pot from the kitchen.— Aeris
- I thought sadism involved being sad and depressed. Obvious, I think.— ]_]
- I thought break dancing involved actually breaking stuff!— Sydle
- I thought that psychological torture involved forcing people to watch really sad movies!— Elviessa
- I'm an American, and for a good long while I thought that Boxing Day involved the sport of boxing.— miss Taken