When you have to go potty really bad but there's no where to relieve yourself.
Little kid:mommy daddy I have to go potty. One of the parents:there's no potty here you'll have to hold t until we get to one. little kid ten minutes later crying: I need to go potty!!! I'm having a potty emergency!!! One of the parents: stop crying before you use the potty in your carseat. Little kid crying:I can't hold it!!!