All thru my childhood I believed that there was a hippopotamus under my bed. I couldn't dangle my legs over the edge of the bed, because she would grab them and haul me under. By the time I was about 7, I imagined she had a baby boy, and if I listened real careful in the early morning, I could hear her explaining to the little one how to grab the legs of children and drag them under the bed (to eat, presumably. :^)
The mother hippo has long since gone but the son grew up as I did. I'm nearly 30, and I still keep a wall/row of boxes on my side of the bed so he can't see if I'm dangling my legs over the edge. I hope he never has children :^)
A childhood belief about under my bed

others believed things like this
- I used to think a female daddy-long-legs was called a "mummy-long-legs".Anon
- when i was little i always asked my mom if my aunt had ant legs or people legs.— kelly
- i used to beleve that the sun had thin long legs and followd me wherever i went..— Hege
- I thought the “Slippery When Wet” traffic sign was a car that had grown long bendy legs.Anon
- I believed that all of my blood was stored in the calves of my legs. — Julia
- I used to believe that if I wet my legs in the sea I would become a mermaid.
— andrea