When I was about 9, I had some friends who found the name "Kevin Traas" scratched onto the door of an old disused toilet at school. They took this to mean that a ghost named Kevin Traas (pronounced "Kevin Trays") lived there.
At playtime they would wander round with a plastic Ghostbuster PKE meter (which they termed an "Amy Peeker") to try and catch him. He even found his way into our creative writing lessons, along the lines of
"I went to scool one day an I found Kevin Traas an he tryed to kill me but I got him with a gun and he was dead"
Our teacher couln't make head or tail of it.
A childhood belief about ghosts

others believed things like this
- I used to think that the lines outlining each of the states found on a US map were really there.— Anna
- When I was a kid I found it hard to say "Sebastian". I always pronounced it "Sebastican". — Dave, Lancashire
- My mom said she had eyes in the back of her head. I looked and looked, but never found them.Anon
- When I was in elementary school I use to think that teacher lived at school at their desks all year long.Anon
- I used to believe that you could catch a bird by putting salt on it's tail— Eli
- I used to think that my teacher lived at school until she came to school late one day. I was shocked!— Wow, you have a life?!