I was about 5-6 years old when I spent the night at an older friend's house. She told me that there were fingernails under the bed that would come out and get me if any body part (like your foot or hand) were hanging over the side of the bed.
This fact was confirmed the following morning while we were making the bed...her cat - hiding under the bed - scratched my foot. I about jumped out of my skin. For years I had to sleep squarely in the middle of the bed.
A childhood belief about under my bed

others believed things like this
- I used to believe that if I scratched one side of my body I had to
scratch the other to be "even".— Greg - When i was little i used to think that my foot was a "naughty part" that no one else was supposed to see.Anon
- I used to belive that if i put my foot in my mouth, I would get foot-and-mouth illness— Emily Sathrota
- When I was little I was conviced if you said twinkee in a mirror 3 time a foot would appear. Anon
- when i was 6 i used to belive if u ate ur toe nails u would grow a foot in ur stomach— chris
- that using athletes foot cream would instantly make me an athlete. — Kate