I used to believe that everyone in the world, when making a sandwich, would only butter one piece of bread. I carried this with me (and made sandwiches this way) until I was about 17 when I just happened to be making a sandwich while I was talking to a friend... he asked me.. "why are you only buttering one piece?" to which I replied "what? thats how sandwiches are made!" I thought it was just a strange thing that my nan did that I picked up on... but no. No one I know does or ever did the same thing.
(I still butter one side)
A childhood belief about general

others believed things like this
- I thought that barf was what they used to make peanut butter and jelly sandwiches!— Maan o' War
- I used to believe that my mother invented peanut butter and jelly sandwiches. Anon
- When I was a little boy, I thought that hair was made out of peanut butter.Anon
- My mother told me if I ate too much butter I'd get worms. I didn't eat too much butter...— Dicky
- I used to think that butterflies made butter— Christophe R.
- I used to think butterflies were made of butter.Anon