Subway riders in New York City and other places around the world on Sunday got an eyeful when their fellow transit users stripped down to their underwear, as a part of the annual No Pants Subway Ride.

The event is organized by the Improv Everywhere comedy collective. It started in 2002 in New York with seven participants.

Steven Blomquist, of Somerville, Mass., center, speaks with Tim Lewis, of Boston, during the No Pants Subway Ride Sunday in Boston. (Steven Seene/Associated Press)

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.

Subway riders in Berlin embraced the pants-free spirit, too. (Maurizio Gambarini/Associated Press)

Participants, who are told to get on trains and act as they normally would, and are given an assigned point at which to take off their pants.

They're asked to keep straight faces and respond matter-of-factly to anyone who asks if they're cold.

Moments before entering a Manhattan station, Peter Saez said it was his third time going pant-less.

"People who don't understand what we're doing will look at us like we're doing something bad or wrong," Saez said. "It's just for fun. It's a fun trip, that's all."

A pants-less passenger waits nonchalantly on a subway platform in Prague, Czech Republic. (Petr David Josek/Associated Press)

Toni Carter planned on stripping down to her boxers with little polka-dots.

"Not very often do I have an opportunity with a group of people to take my pants off and show whatever I got to show," Carter said. "I'm entertaining New York City. This is my form of art."

Participants in Warsaw, Poland, braved freezing winter temperatures to take part in the annual stunt. (Czarek Sokolowski/Associated Press)

Wei Wei, a student from China who just moved to New York, was curious about the event but was on the fence about whether she was going to go through with taking off her pants.

But there was no hesitation for Angela Bancilhon, a tourist from Australia who had her husband and two young sons along for the ride.

"It's fun. Why the hell not?" Bancilhon said. "We're in NYC. Why wouldn't you?"