I'm fairly new to the game, but I've heard many tales of colleagues doing pretty ridiculous things!
A personal favourite of mine, although I don't think it involved too much pain was a colleague doing some work in a roof void- I'm not even sure what he was after up there, but he stepped off the boarded area, straight onto a suspended ceiling. Naturally, he fell straight through, onto the boardroom table, mid board meeting!
Apparently, he simply greeted them with "Good afternoon everyone!", made his excuses and left the room!