When I was 8 or so I read the original story of the nutcracker, E.T.A. Hoffman's "The Nutcracker and the Mouse King", which is a very grim and creepy story. There was a character called the Rat Catcher, and any children up past their bed times when he made his rounds got nabbed, stuffed into a sack and turned into a rat to serve the mouse king. I was always up late into the night, and I knew that one night he would find me out... eek!
A childhood belief about monsters

others believed things like this
- I used to believe that the dancing rats from the nutcracker lived under my dresser.— Molly
- I used to think that when I moved the mouse around on the mouse pad, I was giving the computer a massage.Anon
- i used to think that i was a werewolf and that at night i played poker with the grim reaper— mike
- When I was little and had an ear infection I used to tell my parents I had a mouse in my ear.— Alison
- I used to believe a mouse lemur was a type of a rodent.Anon
- As a child I used to think that the toothy mouse existed.— Jordi Comendador