That's never happened to me, but I came real close to pulling over on the side of the freeway and shitting into a Carl's Jr cup I had sitting in the whip.
100% serious too.
I had the bubble guts so bad I could taste it.
Luckily I was close enough to an exit, and funny thing was that it was a Carl's Jr, and the bathroom was spotless. Didn't even use one of those toilet wax paper things.
But never happened to me while walking down a staircase while I was wearing my denim overalls, I can honestly say.