When I was small, I thought there were 3 types of plug. The electrical kind, the ones in the sink or bath, and the slimy kind that crawl along the ground. My family found this amusing and perpetuated my belief - never referring to them with their proper name "slug".
I can still remember how mortified I was when I discovered the truth at an embarassingly mature age, having made an idiot of myself in front of my schoolfriends!
A childhood belief about creepy crawlies

others believed things like this
- I used to think that if you take the plug out of the bath it will suck you into the bath— awesome kid
- I used to believe that "elemeno P" was a certain kind of "P" found only in the English language. Anon
- I thought the Boogie Man was made of boogers-all green and slimy.— Boo
- when i was around 3 or 4 i belived that the sea had a large plug like a bath and it was draind every night — James Cameron
- I used to believe that once you pulled the plug in the bath a shark would swim out of the drain and eat you.— Amy
- I used to believe that a monster would crawl out of the bath tub and eat me— Alex