NEW YORK - Commuters across the United States shed their pants on Sunday for "No Pants Day."
The event started 8 years ago in New York City where participants with bare legs were required to mingle with other-- equally half-naked-- travelers.
The annual event encourages riders to strip down to their underwear as they go about their normal routine.
The event's organizers, Improv Everywhere, said that as many as 3,000 people participated in the "No Pants Day" event in New York alone, with more participating in 3 other cities.
According to its official website, Improv Everywhere is a long form improvisation troupe that executes pre-planned "missions" or performances that usually involve socially awkward or unusual situations.
Some commuters who participated in "No Pants Day" said they got phone calls from friends or invitations to join the event on Facebook.
"No Pants Day" was celebrated in 44 transit systems in 16 countries.
Improv Everywhere was behind internet video sensations like "Frozen Grand Central", where 200 performance artists "froze" in their positions for a few minutes, causing a stir in New York's Grand Central Station.
They were also behind "Food Court Musical" where certain employees and diners at a food court suddenly broke into song and dance, surprising diners and mall-goers who were not in the know.
The group, formed by Charlie Todd in 2001, has reportedly executed over 100 "missions." With a report from Reuters and CNN.