You can actually see documentation of the no-pants celebrations in the no-pants photo gallery... I was going to put up a few, but, after some careful consideration I decided that posting pictures of strangers in their underwear is just not really my bag. So, you'll have to go forth and forage for pics yourself.
I realize you may be thinking things like... so, if I have no pants on, then where do I keep my pocket lint? Or, if I have no pants on, and my shoes don't have to match my belt, do I have to match them to something else or does everything just devolve into complete chaos? Or, if NO ONE has pants on (not just young hot people, but all people), do I even want to go out of the house? The FAQ answers some of these kinds of burning issues, for instance-- "haha, you only said no PANTS, so can I wear a kilt instead?" (the answer is no, you wiley wiley cheater)
If you ARE debating what outfit to wear, they have kindly supplied a quiz. I, apparently, will be wearing a lovely pair of boxers. Keep your eye out!