No Pants Subway Ride, created by a group called Improv Everywhere. The idea: all afternoon, board mass transit in your skivvies. Undergarments were required, mind you.
Participants spread out over six meeting points and 10 subway lines during the mild 44-degree day, with more than 4,000 taking part in the frolick fest. Now that's my kind of ride.
The No Pants phenomenon has since been copied in 59 cities in 27 countries around the world... because as we all know: If it's worth doing, it probably started in New York City. (Photos: Improv Everywhere, Google, Flickr)