Riders strip on NYC subways

Thousands of people participated in the 12th annual No Pants Subway Ride, organized by New York City prank collective Improv Everywhere. During the afternoon winter event, participants boarded separate subway stops and removed their pants, pretending that they did not know each other. The event, referred to as a "celebration of silliness" is designed to make fellow subway riders laugh and smile. In this photo, a woman rides the subway pantless on Jan. 13, 2013, in New York City.

Some riders in the New York City subway in the underwear as the take part in the 2013 No Pants Subway Ride on Jan. 13, 2013.

People ride the subway pantless on Jan. 13, 2013, in New York City.

A pantless woman stands on a subway platform on Jan. 13, 2013, in New York City.

Some riders in the New York City subway in the underwear as the take part in the 2013 No Pants Subway Ride on Jan. 13, 2013.

A soldier takes off his pants while riding the subway on Jan. 13, 2013, in New York City.

A soldier removes his pants on the subway on Jan. 13, 2013, in New York City.

Pantless people stand on a subway platform on Jan. 13, 2013 in New York City.

One subway passenger sleeps as others ride the train pantless on Jan. 13, 2013, in New York City.

Some riders in the New York City subway in the underwear as the take part in the 2013 No Pants Subway Ride on Jan. 13, 2013.

Pantless people pose for photos at the Union Square subway station on Jan. 13, 2013, in New York City.

A pantless man knits at the Union Square subway station on Jan. 13, 2013, in New York City.

Some riders in the New York City subway in the underwear as the take part in the 2013 No Pants Subway Ride on Jan. 13, 2013.