Jolie Lee

USA TODAY Network

Don't be surprised if you see a lot of bare legs on the subway this weekend.

Jan. 12 is No Pants Subway Ride day, an annual event celebrating silliness.

Started in 2002 by the New York-based group Improv Everywhere, this day of riding public transportation pants-less has spread to nearly 60 cities worldwide in 26 countries.

As the name of the event implies, participants dress in normal winter attire — coats, hats and scarves. The only thing missing is their pants.

The event is not about exhibitionism but comedy, said Charlie Todd, founder of Improv Everywhere, in an interview with USA TODAY Network.

"It's meant to be a positive thing to make people laugh and smile," Todd said.

Last year's No Pants Subway Ride in New York had more than 4,000 participants, he said. Todd said he believes the event there is a "rite of passage" for city residents.

Chicago's No Pants organizers recommend wearing "granny panties, boxer briefs, boxers, boy cut." In other words, something that is "tasteful and covers more," according to its Facebook page.

Washington's organizers remind participants to act normal, "as if you had no idea that you were missing pants or that you knew but didn't think it was a big deal," according to the D.C. Facebook page.

People generally laugh and take pictures when they see the pants-less passengers. Some even respond by taking off their own pants, Todd said.

"If you're the only one in a car with pants on, suddenly you're the odd one out," he said.

D.C.'s organizers also tell participants to put their pants back on if an authority tells them to.

"Unfortunately, indecency laws are entirely subjective," their Facebook page said.