Feeling bold? This Sunday (Jan 12) is Philly's annual No Pants Subway Ride. Yep, where you literally get on a train and ride around, without your pants (please wear some sort of underwear so you don't get arrested for indecent exposure...sorry, but I'm not bailing you out)
Most years you'd have to worry about freezing your behind off, but with the predicted high of around 70 degrees on Sunday, that's something you won't have to worry about.
The event organizers, Disability Pride Philadelphia, will be collecting socks to donate to the homeless at the meeting place before the ride. Meet up is at The Clothespin Stature at 5th & Market at 3pm, the event is scheduled to run from 3-5. I have not personally attendee one of these before, but it seems protocol is to wear pants until you get on the subway, then drop them once you're aboard.
The No Pants Subway Ride is an annual global event started by Improv Everywhere in New York in 2002. http://improveverywhere.com