As

is by now traditional, not actually something that happened to me, but when I was at uni, our wildly out-of-the-way campus was visited by a rugby team from either Oxford or Cambridge, can't remember which now. At the regular Friday night disco in one of the rancid nearby towns, I nipped into the gent's for a jimmy just in time to see one of the visiting rugger buggers shitting in a urinal. Which wasn't exactly the funniest thing in the world ever, at first. But it rapidly became very funny indeed when the urinals picked that precise moment to flush, and he ended up with several pints of water and a number of rapidly-disintegrating stools dumped over his trousers.

A good mate worked as a barmaid/cleaner in the same venue and once found one of the cubicles in the gents liberally smeared with poo... and with a couple of nice firm turds neatly deposited on a sheet of newspaper in the corner.