woah, that's a tough one... but probably the time me and my friend decided at 2:30 am to go dancing on main street in our undies. we brought a stereo and everything! and we danced with tree branches.
Walked naked out of a pub on Stockton High Street at around 17.30 in the pouring rain, around the pub and back in the through the fire exit.
OR:
Fell asleep in the same pub a couple of years ago, woke up, had a wee against the bar and went back to sleep.
Stopped drinking now, you'll be glad to hear!
I've been thinking about this for myself but I honestly can't think of anything. I know I've done little crazy things throughout my life but nothing springs to mind.