Not just shitting, I suppose we can have pissing as well.
Shitting: A youth at my school (who was very very disturbed...had some horrible family traumas, and eventually got sent away for burgling an old people's home. I could write a book about this kid. He was fucking NUTS!) once ate 2 packets of those sugar-free mints before first break. These mints were new on the market, and the great gimmick for a 13 year old lad was the fact that they had a laxative effect. If you had a few mints you could fart loudly and frequently. The lad was farting like a motherfucker all morning in a most antisocial manner. Just before first break he squeezed out a really raucous one, like "LISTEN TO THIS!", and predictably followed through. He shat his damn pants like a good 'un! He was wearing tight-ass Sta-Prest trousers which obviously helped spread the muck, adding to his discomfort. He had to run home at break to change his shitty pants and trousers. Later that day he was sat at a desk - his trousers were too short, producing a 'half-mast' effect. We noticed he had foolishly neglected to change his socks - his white sports socks were streaked with brown!
This same youth did a shit in an eggbox on the top floor of a multi-storey car park. I was with him, dammit! He pulled his boxers and tight jeans up WITHOUT WIPING HIS ARSE (fuckin grim) then threw the shit-filled egg box off the side of the building. It landed outside the supermarket entrance (the supermarket was open) and splattered out to a radius of about 10 feet. It may well have splattered onto shoppers.
He also did a shit and threw it against the wall of a bus shelter. And did a shit into the river, hanging off a discharge pipe. He also ran down the high street on a busy Saturday afternoon with his pants and trousers down, the fucking freak. And (not toilet-related), he burgled his mate's house on Christmas eve, stealing the wrapped presents from under the tree, then gave them to his own family, randomly, without unwrapping them, so his mum got an Action Man or some shit, his brother got some curling tongs, etc. I'd love to know what he's up to nowadays...
As for pissing: I was out boozing with some friends, at about age 19. We were staying at a friend's house, who's parents were staunch (but sound) Christian schoolteachers. I got fucking ruined and had a blackout. Me and my pal were staying in the study, where the parents marked the schoolwork. I (apparently) woke up in the middle of the night and got up and started "sleep-pissing". My mate was like (incredulously) "What are you doing???" to which I replied "I'm having a piss". I went back to sleep, and when I awoke discovered I had pissed all over a table full of important GCSE work, soaking it with booze-piss. We had to spend the next day sat around the house watching TV with the kid's parents. The piss incident was not directly mentioned but fucking hell, I was fairly embarassed, eh...