At the booming command of a voice through a bullhorn, about 100 pairs of jeans, sweatpants and skirts were dropped to the floor.

The No Pants Subway Ride, a surprisingly organized and well-attended annual goof, kicked off Sunday afternoon despite the frigid temperatures.

Dozens of GTA residents, of all ages, body types and degrees of immodesty hopped on the TTC’s Line 1 at Finch Station, bound for the city’s west end.

“It’s a bucket list (goal),” said Janice Sinclaire, going pantsless to celebrate her birthday. “If you want to have a memorable birthday and do something unique, well, this is pretty well at the top of the chain.”

As half the train crammed with the no-pants people, briefs mingled with boxers and impromptu dance parties broke out up and down the train. Selfies were snapped. At least one gymnastics routine was attempted (with mixed results) on one of the poles.

For Michael Ishlove and Georgia Peters, who first rode bottomless on the Rocket two years ago, the biggest draw is the reaction from the full-clothed public.

“It’s fun,” said Peters. “What we found very interesting the first time we did it was watching the people getting on the subway and going ‘What the . . . ?’ ”

Torontonians weren’t the only ones undressing down to their drawers Sunday.

Subway riders in 31 other cities around the world took part in the No Pants Subway Ride, founded in New York in 2002 by public space comedy group Improv Everywhere.

Toronto’s pantsless horde rode the Yonge Subway around the loop, past Union and up to Line 2, where they switched trains and headed for Dufferin Station. Then, a chilly march to Penny’s bar — near Bloor St W. and Lansdowne Ave. for a No Pants party.

“It’s something different,” said Ishlove. “Something outside the normal everyday.”

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Photos: No Pants Subway Rides from across the globe