I used to believe that farts were actually triangular brown things that floated out of your arsehole - despite the fact that no one, myself included, could see them, I was still convinced of that fact until I was about 4.
A childhood belief about farting

others believed things like this
- I used to believe that farts were triangular with the ends rounded so they wounded hurt.Anon
- I am Catholic. I used to believe that the Father presenting the Mass was in fact God himself.— Lindsey
- I always pictured the good Samaritan as a Samurai. Still do, in fact.Anon
- i used to think that the red colourin gon Smarties was made from Beatles blood. In fact, I still do!!— pigsy
- I recently very disturbed to learn that Al Jolson was in fact Caucasian.Anon
- I used the scar on my dads leg was a shark bite when in fact he fell off his bike when he was a child— Wendy Murray