At a young age, I was under the belief that having sex had something to do with kissing after you were married, that there was some magical type of kiss you could perform to make babies.
I also believed that if you positioned yourself right, you could possibly have a child without the opposite gender's involvement. This, in my mind, explained same sex couples, The Immaculate Conception, and Anakin Skywalker's mother (In Episode One, I clearly remember one of the jedi asking her, "Who is the father?" and her reply of "There isn't one." I took this extemely literally).
A childhood belief about giving birth

others believed things like this
- I used to think you could be gay or lesbian from kissing your own family members of the same gender.Anon
- I Use to that all couples got married twice to renew the marriage
— Lucas Jr fique Marti d - I used to believe that if I could kiss my elbow that I would turn into a girl (the opposite sex).— Rusty
- When I was very young, I thought that God was married to Mother Nature, and that together they made weather.Anon
- I used to believe that babies came out of your belly button. What else could they possibly be for? — Andrea
- I thought that only the mother made the child, the father was an "extra" in this area— Lea Weiss