I think it's funny when...

girls carry their purses to the restroom as if that’s more subtle than clutching a tampon in their hand. Or stuffing it in your bra or something. To every other girl in the room it’s like *ding*ding* youuuuu’re on your period.
I find it even funnier when men will ask, where are you going? Those girls will tell them, to the bathroom and then the men look at them completely perplexed.