When ones bowels suddenly revolt and overthrow the status quo of unsoiled pants.
Oh man, you better pull over here! I think that shrimp at Cap'n D's was bad and I'm about to have a poo d'etat in my pants.
When you really really have to take a shit so you're rushing to get home so you put the brown siren on top of your car to let everyone know to get out of your way.
Robert: Shit! Why did we have to go to the Indian restaurant on the other side of town. I don't think I'm gonna make it home. Put on the brown siren for fucks sake!