Gone to an OB appointment where they ask you for a urine sample. You don't really have to pee, so you try to catch every single drop. You're pretty satisfied with your measly quarter cup, but then you spill more than half of it all over yourself. Then you have to walk out with a huge, wet, pee mark on your jeans and a cup with less than a quarter-inch of urine in it.
Yeah, that's never happened to me either.