Before I learned about how men have testicles, maybe up until the age of 8, I thoight that men just had a penis with a bunch of hair around it, and nothing else, and was always very baffled when I heard people referring to a guys "balls".
Now the funnier part- when I did eventually learn about testicles, I did not know about the "sack" that they are in, and I thought that they were just these two hollow "balls" stuck behind the guy's penis...
A childhood belief about rude bits

others believed things like this
- I originally thought "balls" was slang for buttocks instead of testicles.Anon
- i used believe and erection was when your testicles went into your penisAnon
- I used to think that girls had "balls" and not boys, and the "balls" were slang for breastsAnon
- i use to believe guys could have a random # of balls but the maximum was 4— bookie
- I used to believe that gay guys had sex by sticking their penis in the other's penis.— Fanbrat
- i always thought it was Grape Balls of Fire instead of Great Balls of Fire— Courtney