A little disgusting, but...
When I was about 8, my mother had just recently given me the good old puberty education, including the joys of having my very own period. One of the things I learned is that girls had periods so that they could pass their unfertilized eggs out of their bodies. Well, one day, I took a shower and she went to the bathroom, so she didn't flush (poor plumbing, thus I would have been burned by scalding hot water). When I got out to dry, I peeked in the toilet and saw it was red inside - plus there was this really big dark thing! For days, I was in a panic about having my period, because I didn't want to pass that HUGE thing through you know where!
... then I realized it was poo I had seen, and not some huge unfertilized egg. I was so relieved to learn that the eggs were microscopic...
A childhood belief about periods

others believed things like this
- I used to believe the Do Not Pass signs on the roads meant you were'nt aloud to pass the sign. I was 14.Anon
- I used to believe that only brown eggs came from chickens. I thought white eggs were made at the store— Destiny
- When I was a kid, I used to believe that cadbury cream eggs real uncooked eggs in the middle Anon
- I used to believe that you could pass things down the telephone.Anon
- that cats were only girls and dogs were only boys. I definetly didn't get the whole reproducing thing yet.— Jamie
- i used to believe girls laid eggs — Bill