I'm obviously coming a little late to the party here, but I've just seen my new favorite Improv Everywhere mission. If you don't know Improv Everywhere, take a second and check out their website, because they really are more fun than should probably be legal. Every year they bring us the No Pants Subway Ride, among other absurd stunts, all of which increase the sum total of joy in the world. Because I was not paying attention, I missed this one:
Thanks to Zach for the email!