I couldn’t think of anything until I read @Cupcake‘s answer, and then I remembered…
When I was in kindergarten, I got a book that answered a question for every day of the year. My parents meant to read it with me, one day at a time, as the format suggested, but I was impatient and wanted to know everything right away, so I skipped ahead and read the ones that interested me on my own. One of these included “How are babies made?”
As I recall, the answer was your typical “When a mommy and a daddy love each other very much…” type of thing. It said that when people love each other, they want to show each other by being close, and that the man will put his penis between the woman’s legs and move. So I spent a couple of years under the impression that girls had to close their legs and guys would put their penis between her thighs and just hump away.
(When I was in second grade, I got another similar book, only this one was more descriptive, and then I understood how it was supposed to be done. I never fully trusted anything from that first book again!)