I used to believe:
* Someone, somewhere, was capable of reading my thoughts, so I tried not to think about things I wanted to keep secret, in case this imaginary psychic person turned out to be someone I knew. (Weird, I know.)
* Babies grew inside of a woman's stomach (it seems logical when you look at a pregnant woman, especially when people tell little kids that the baby is in the woman's "tummy").
* Before I knew about sex, I thought that women just magically got pregnant when a man and woman "really loved each other." I guess I thought that if you thought about wanting a baby, you'd suddenly be pregnant. I don't really remember the details of this childhood belief, but it was something like that.