I believed it to be an absolute fact that all cats are female and all dogs are male. I had no idea how reproduction worked at this point, so it just made sense to me.
Then one day, a classmate was talking about her cat and how "HE" had done something funny. I had to clarify, "Your cat is a boy?!?" and my entire understanding of animals was shattered that day.
That's why American conservative patriots love eagles so much