As a child I believed that toilets were alive. When you used them, you were feeding them, and if they didn't like what you fed them, they'd vomit it back up (overflow). If you made them angry, they would eat you, so you had to be nice to them and not make them sick. Stranger-toilets (e.g. public restrooms) were especially untrustworthy - best to keep an eye on them at all times.
I also believed that they would detach from the wall and dance around the bathroom at night when no one was around. You couldn't normally catch them at this, because they'd go back to being inert as soon as they heard you coming, but if you closed the bathroom door and then quietly crawled up to it and looked under the bottom, you could see this happening.
A childhood belief about fear of

others believed things like this
- I thought the "To Let" signs on buildings meant they were public toilets.— Scottish Laddie
- I used to think that in public toilets, the cleaning lady actually lived in the supply cupboard.Anon
- I believed alligators lived in toilets, and one apparently got hold of my sister.Anon
- When I was little, I believed that if I didn't go to the bathroom quick enough, I would actually explode.— Coco S.
- I used to believe my barbies came alive at night, so I would always try to catch them in the act.Anon
- i used to be scared to use the bathroom becuase i believed something lived in the toilet.— robert allen freeman the fourth