Yesterday was International No Pants Day, though you'd be hard-pressed to find it printed on any official calendars. With 16 countries and 44 cities participating, thousands of people boarded subway systems around the world to pull off one of the biggest annual pranks by taking off their pants. (Note: everyone wore underwear.) We talk with Improv Everywhere's senior agent Alex Scrodelis about the 9th annual ?No Pants Subway Ride,? in which close to 3,000 New Yorkers participated and cities as far off as Zurich, Australia, Argentina and Spain all saw pantsless pranksters riding public transportation.