You know when kids have finished brushing their teeth they put the brush under the tap and then suck all the water from it? Probably not, but when I was younger I thought that you could only do that 5 times if you were 5, 6 times if you were 6, and so on, if you did any more your toothbrush would be taken away from you. Obviously.
A childhood belief about bathrooms

others believed things like this
- When I was younger, I believed that times tables in maths were kids sitting at tables staring at clocks!Anon
- I used to believe that eating burnt toast would make your teeth whiter and would brush your teeth for you.— Natasha
- I used to believe that if I didn't brush my teeth at night, ants would crawl into my mouth and eat my teeth.Anon
- I thought "Angel of the Moring", by Juice Newton said "just brush me teeth before you leave me"!!!Anon
- I used to think that "One, two, three times a lady"
was: "one, two, three times related"Anon - I used to believe when i was about 4 (now 15) that dinosours died because they didn't brush their teeth— gullable