I used to believe that hallowen costumes were real monsters and not costumes and that's why I didn't like going out too much at night on Halloween, other things that I believe was that If I stayed awake at Christmas, Santa Claus would leave me nothing because I was going to see him.
A childhood belief about monsters

others believed things like this
- When I was a kid I used to believe that cartoons were people dressed up in special costumes.— Sarah-Jane
- I used to believe that the "real" Santa Claus was at Macy's in New York City. All the rest were fakes. — Marcia
- I was told that for every christmas carol i sang before christmas time santa would give me one less present!— K
- I used to believe that, if God would die, Santa Claus would be boss.— Judith
- I used to believe that the Holy Trinity was Dad, God and Santa Claus!— Cathy P.
- When i was little, i thought Santa Claus was my grandfather— Junie