No Pants Subway Ride 2013: The day no one wore pants to work

It started off as a prank and became a rage over the years, drawing flak from some and amusement from others. Here are some pictures of the 12th Annual No Pants Day.

A man, wearing underwear, records video of another man, also wearing underwear, during the annual 'No Pants Subway Ride' at a subway station in Mexico City

Carrying a bike, a participant in the annual 'No Pants Subway Ride' transfers to another train in Mexico City

Participants in the annual 'No Pants Subway Ride' ride a train in Mexico City, Sunday, Jan. 13

The prank was initially staged by seven New York entertainers from the group Improv Everywhere in 2002.

"The idea behind No Pants is simple: Random passengers board a subway car at separate stops in the middle of winter without pants," the group's website says.

Participants in the annual 'No Pants Subway Ride' wait to get a train at a subway station in Mexico City, Sunday, Jan. 13, 2013.

Participants take part in the annual 'No Pants Subway Ride' in Stockholm, January 13, 2013. The event involves participants who strip down to their underwear as they go about their normal routine.

Passengers react to seeing a man take off his pants on the subway during the annual 'No Pants Subway Ride' in Shanghai.

A man not wearing pants waits on the subway station during the annual 'No Pants Subway Ride' in Sofia.

Men not wearing pants take part in the annual 'No Pants Subway Ride' in Sofia January 13, 2013.

People without their pants wait for a subway train during the 'No Pants Subway Ride' in Berlin.

People without their pants wait for a subway train during the 'No Pants Subway Ride' in Berlin.

People watch as participants in the 'No Pants Subway Ride' take the 6 train downtown in New York.

People without their pants arrive for the train during the 'No Pants Subway Ride' in Mexico City.

This man doesn't seem to amused by a participant of the 'No Pants Subway Ride' in New York City.

Men swing on a pole in Union Square park after the 'No Pants Subway Ride' in New York.