My mom gave birth to my younger sister at home. I watched. I was 2.

For some reason that I still don't understand, my mom thought it was important that I know the proper terminology for everything I was going to see. Several months later we were in line at a McDonald's when an obese woman walked in. I loudly announced: "I BET THAT LADY HAS A BIG VAGINA."

My mother was absolutely mortified.