1) One day during break I ran into a kindergarten student at my school named Eric Li coming out of the bathroom. He did this double take and then ran out to the front desk anonouncing “老師上了廁所。" The teacher went to the bathroom! I forgot that at the age of six, you don't know your teachers are real people who sometimes use the bathroom.
2) Hiccoughs in class. It's ok if you're a student and you hiccough. But a teacher isn't supposed to get them. I've had them in class. It's not fun.