Some time well before puberty, I used to wake up with a hard-on in the morning. As I usually had to pee in the morning, I put two and two together and decided the hard-ons were due to my penis getting filled up with urine overnight.
A childhood belief about rude bits

others believed things like this
- I used to believe that I was born from an egg and would wonder if I had a hard time pecking put of my egg— Cheryl coffman
- The sun switches off at night and on again in the morning — Edward
- i used to think that PMS stood for "pregnancy morning sickness".— confused little girl
- when i was a kid, i used to think that if i didn't fall asleep, morning wouldn't comeAnon
- i used to believe that the water in the ocean went away a night......then came back in the morning.— Beverly
- when i was small, i thought if i don't sleep then morning wouldn't come..— lily