Thousands go pant-less for 2013 No Pants Subway Ride

Thousands of people in New York and around the world rode the subway in their underwear on Sunday in the name of an important message: It's funny when people take their pants off.

The self-described 'prank collective' Improv Everywhere has organized the No Pants Subway Ride each year since 2002. More than 4000 brave souls did the pant-less subway ride this year, according to Improv Everywhere.

[ Photos: No pants? No problem ]

The joke has spread to countries outside of the U.S. too, including Canada and Mexico. Toronto's event reportedly had about 60 participants but Vancouver shocked riders of the SkyTrain by gathering hundreds of participants, according to Postmedia.

Riders are told to act casually when people stare at their bare legs and pretend they haven't noticed the crowd of pant-less people around them. For example, they could say something like, "Oh, what's that you say? I'm not wearing pants? Oh dear, well I suppose you're right."

One Vancouver participant said he tells people he simply forgot his pants today.

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The only purpose of the event is to earn a laugh from puzzled onlookers and have fun. An unintentional purpose, perhaps, is showcasing interesting underwear fashion choices. Polka dots and smiley faces might be all the rage this season but classic grey, white and black still prevail.