I used to believe that the way you had sex was to take off your shirt and show your chest muscles - this would make the woman excited and she would want to press herself against you (fully clothed) and kiss you, thereby getting pregnant. You did not make her pregnant if you were wearing your shirt.
I attribute this belief to way too many Hercules and Sinbad movies as a child.
A childhood belief about sex

others believed things like this
- That to make a baby a man (over 21 & under 25) had to kiss a woman (over 19 & under 21).— Johny
- Until about the age of 13 i used to think that oral sex was 'normal sex' but fully clothed!!— Daveyd
- I used to believe that eating too many tomatoes could make you pregnant.— Mariah
- i used to believe that if u kissed a boy u would get pregnant.i was scared when i had my first kiss.— imbrressed
- Years ago, when I was youger,I used to believe that we just needed a kiss to get pregnant— Candice
- When you saw a funeral go by, you had to grab a button on your shirt.Anon