After seeing the film Batman i was sure that if you flushed the toilet and didn't leave the room at full pace the penguin would pop up (riding a giant rubber duck) and eat your face.
A childhood belief about fear of

others believed things like this
- I used to believe that Limabeans would kill you if you didn't eat them.
I flushed them down the toilet.— Lima - i thought that "aromatic" duck was actually "asthmatic" duck.
poor thing...— rachael - I always thought that duck sauce (from chinese restaurants) was duck poop.
— emily - my friend thought that the film 'the hulk' was about the jolly green giant from the sweetcorn adverts.— patticus
- I used to believe that monsters lived in my toilet and they ate my poop and urine when i flushed the toilet.Anon
- I used to believe that if I flushed the toilet before I showered, I would take a shower in dirty toilet water.— Chris D