I used to believe that I had elves and pixies living under my bed, and that they would only come out at night and that they would only talk to me. I was absolutely convinced and thought that the reason that I couldn't actually remember talking to them the next morning was that they must have brainwashed me (kind of Men In Black-style) so that I couldn't tell anyone about them.
A childhood belief about under my bed

others believed things like this
- I can remember thinking that is I hid my eyes, and couldn't see anybody that they couldn't see me.Anon
- a friend was convinced that his school was an asylum, and couldn't be convinced otherwiseAnon
- I used to believe an "Ego" was a kind of hair style, similar to a mullet.Anon
- I used to think that singers couldn't talk-they could only communicate by singing.Anon
- When I was a year old, I believed if I hid my face, my mother couldn't see me because I couldn't see her.— kimberly dianne(:
- I used to think that dreams were events that really happened, I just couldn't remember them when I was awake.— Warren