When I was five or six, I was watching TV (I think it was "The Simpsons") and a character mentioned a piece of paper but I misheard and thought she (I'm pretty sure it was a woman) said, "piece of *vapour*".
A childhood belief about speaking

others believed things like this
- I used to believe fax machines instantly teleported a piece of paper to who ever you wanted. Anon
- I used to believe Jessica Simpson was a secret character from "The Simpsons"— Lemon Jelly
- I thought Spongebob Squarepants was a piece of Swiss cheese.— Melanie
- i used to believe that one piece of ear wax was actually called a wach. — rachael
- I used to think that a gherkin was some kind of piece of machinery. I wonder where I got THAT from...— Some Idiot
- I used to be scared that if I chewed my cuticles and swallowed a piece of skin, I would become a cannibal. Anon