When I was passing the sponsorship form round at work, as a joke one of the girls wrote "naked" next to the description of the parachute jump I'm doing. I crossed it out of course, because there's no way I would ever do a parachute jump in the nude - and certainly not in the climate of the North of England. Not everyone's as sensible as me, though. I found this video of some crazy Germans doing a mass nude skydive on YouTube:
I don't know why people think Germans are humourless, they'll obviously do anything for a laugh!