A friend of mine told his niece about "Sister". A girl who shows up in your bedroom at night. He told his niece that if she sees her to throw a blanket over her and run to her parent bedroom and tell them. Needless to say his sister and brother-in-law were awakened several times in the middle of the night.
A childhood belief about monsters

others believed things like this
- My friend's sister believed the lyrics to Gazza's "Fog on the Tyne" were "Fog on the dinasaurs mine all mine"— Suzanne
- My niece used to believe that I lived in the sky because she always saw me leave for school on an airplane.Anon
- My friend's mom told my friend's little sister thatI when a dog died, it went to a retirement home.— ellen
- My niece used to call Marmite Falloy! Where she got the word Falloy from nobody knows— Russ
- I used to think that Cain and Able were brother and sister (with Able being the girl).— Duh
- i used to think that my sister was a genie and flew a magic carpet at nightAnon