My ex and I had an argument once. She was the type that loved to find things to fight about and one day she convinced herself that I was sterile. I did the home sperm count test thing and while it didn't come out bright blue, I had a slightly below average count at worst (and I didn't wait the three days, was playing basketball daily, with long hot showers, etc...). She insisted the test indicated I was sterile, I was probably also color-blind, she raised doubts about my long-term worth as a suitor, etc....
Anyway, we broke up about six months afterwards (looks and sense of humor only go so far). It turns out that despite the fact that she was on birth control & ritalin, I usually pulled out, and we were both drinking heavily, I got her pregnant. Luckily, it aborted itself.