Until I was about 5 or 6 I used to believe that the area of the moon that you can't see when it's not full just wasn't there. I learned it from Bugs Bunny cartoons.
A childhood belief about outer space

others believed things like this
- The moon is full of wotsits.Anon
- I used to believe that the full moon was God's flashlight.Anon
- i used to believe the easter bunny was my bunny that a fairy turned real.— Twix
- I used to believe that bunny rabbits hatched from eggs, since the Easter Bunny gave you eggs.— goat
- i used to think that the moon would follow you in the car, also that it looked like a half moon.— natalie k
- I used to believe that Moon is the kid of Sun, because it has less light and Moon smiles with kids. — Syed Arbab Ahmed