I believed that a platypus lived under my bed. Well, maybe I didn't actually believe it, but it might have been possible, and one can't be too careful about such things, can one? Anyway, it could climb up if I let the bedclothes touch the floor, so I made sure everything was tucked in. A male platypus has poison "spurs", so it's good to make sure one can't get into your bed.
A childhood belief about under my bed

others believed things like this
- I used to believe that ear wigs would climb in your ears while you slept and make you go mad— troy
- when i was a kid i believed i could make things happen just by snapping my fingers like in mary poppins!!Anon
- i believed that carrots with milk was a deadly poison until i was 11.— Jennifer
- I'm deaf in one ear. Until I was 7 I believed that if I didn't sleep on my good ear, dinosaurs would eat me.Anon
- I used to believe that the people that worked in stores slept right there on the floor and lived there. Anon
- I thought the word mailman was male man and it seemed dumb to me as aren't all men male?— andalite