- I thought a condom was just a short thing you put on the end of a guy's penis. I didn't realise you had to roll it all the way down.
- I thought an erection continually went up, down, up, down. I could never see how this could help with reproduction and a few years later my mind was put to rest when I discovered that an erection stays up for, well, however long... and when it goes down the erection is over.