Participants in the No Pants Subway Ride wait for a train in their underwear in New York’s subway system Jan. 11, 2015. Getty Images

One day each year, subway riders band together to make their commutes a little stranger than usual, as many participate in the annual No Pants Subway Ride. Passengers will brave the cold and leave their pants at home Sunday in more than 60 cities around the world, including Boston, London and New York.

What began as a prank by seven guys in 2002 has now ballooned into an event that spans more than 25 countries. The yearly event has even given rise to a documentary feature “We Cause Scenes,” which is available through Netflix.

Every January, the group Improv Everywhere organizes the No Pants Subway Ride. In New York, thousands of people participate in the event. They are requested to keep straight faces as they embark on their pantsless subway rides.

“The idea behind No Pants is simple: Random passengers board a subway car at separate stops in the middle of winter without pants,” the organizers said on the event site. “The participants behave as if they do not know each other, and they all wear winter coats, hats, scarves and gloves. The only unusual thing is their lack of pants.”

More than 7,000 people have signed up for Sunday through the No Pants Subway Ride 2016 page on Facebook. All the New York participants are asked to show up at one of the seven different meeting places around the city at 3 p.m. EST. The meeting places include the Hoyt Playground in Astoria, Queens; the Old Stone House in Brooklyn; and Foley Square in Manhattan.

“I think part of [the event’s appeal] is that it’s just such a simple idea,” Improv Everywhere founder Charlie Todd told the Huffington Post. “Everyone can get on board with people riding the subway pantsless in the middle of winter. The juxtaposition of the winter coats, hats and gloves with bare legs is something that’s immediately striking.”

Organizers advise participants that if anybody inquires about their lack of pants, tell him or her they were “getting uncomfortable.”