CHICAGO, IL -- Subway riders in other cities around the world got an eyeful when their fellow transit users stripped down to their underwear.
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The annual No Pants Subway Ride took place on Sunday.
The event is organized by the Improv Everywhere comedy collective. It started in 2002 in New York with seven participants.
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Organizers say pants-less subway rides were scheduled to take place this year in dozens of cities around the world. Philadelphia's version is sponsored by a laundry delivery service.
Participants are told to get on trains and act as they normally would and are given an assigned point to take off their pants. They're asked to keep a straight face and respond matter-of-factly to anyone who asks them if they're cold.
Photos: Thousands turn out for 'No Pants Subway Ride' in New York
Annual 'No Pants Subway Ride' hits cities around the world