Mine wasn't so terrible, mostly because I decided I could hold it for the rest of the ride after all.
I'm on a bus going across the desert in the western (Muslim) part of China. The bus stops at the only building I've seen since getting on. It turns out to be a fairly newly constructed restroom, a roundish windowless concrete building. We hadn't seen a soul in hours, and there was certainly no one else around as the bus pulled up, and nothing else around.
I walk in and it's one big room, floor, ceiling, and walls, that's it. And a row of slits on the floor with a bunch of guys (who, reflecting back, more or less look like bin Laden - robes, beards, sandals) hunched over them, each holding a clay jug, and all eyes on me. Since there wasn't a sink or running water, and I didn't have a clay jug, well, I didn't ask the driver to pull over in the first place..