They got on the New York subway trains just like any other commuters in the early January cold. Then, they calmly removed their pants, folded them up, and continued their ride as if nothing unusual was happening.

They were the participants in an event started in 2002 by the improvisational theater group Improve Everywhere: the No Pants Subway Ride, according to AP. Participants met at six locations throughout the city to board the trains, then split up into groups and soon stripped down to their underwear. Once the pants were off, the participants continued to read magazines and chat regardless of the reactions from other riders.

The event has become so popular that it has spread to other cities, and pants-less riders were reported on Phoenix's Metro Light Rail, as well. "Arizona's too hot to wear pants," one half-naked rider told a fellow commuter when asked what was going on, according to KPHO-TV.