When I was about 5 I saw something on a public television show about jaundice. My mom told me that people turned yellow when they couldn't pee! (Apparently she didn't want to discuss kidney failure... go figure.)
Then I got that mixed up with another show about the Masai people and how they drink cow blood and urine (that's what I heard at the time, anyway). Somehow, I believed that if you peed, got any urine on your hands while cleaning up, forgot to wash your hands and then ate something, then the urine would get in your mouth, you would turn yellow, and die.
My parents took me to the doctor to try to sort out why I had a rash on my hands from washing them over and over (at least 30 times a day). When they told me to stop washing my hands so much, I thought they were trying to kill me with my own urine.
A childhood belief about weeing and pooing

others believed things like this
- i knew that if you ate beets your urine would turn pink and i thought if it was pink, then you could drink it.— JP
- I used to think that when it rained,it meant God was washing his hands Anon
- When I was little I thought that my urine was stored in my scrotum until I needed to wee.— Bryan
- I used to think that tampons were meant to absorb women's urine so they wouldn't have to go to the bathroom.— Koyaanisqatsi
- I used to believe that my urine was a super fertilizer - peeing on plants made them grow.— Andrew C
- I used to believe that monsters lived in my toilet and they ate my poop and urine when i flushed the toilet.Anon