Thousands of commuters ride bare-legged for No Pants Day

Hairy thighs, pale calves, and polka dot underwear. There was no shame for the thousands of commuters around the world who travelled sans trousers for the 14th No Pants Subway Ride and its variants on Sunday.

What began as a small stunt by seven New York subway riders in 2002 has turned into a global event. The original pranksters, who formed the group Improv Everywhere, said pants were dropped and legs bared in 60 cities, including London, Hong Kong and Johannesburg.

"It's a celebration of silliness," said Larry Piche, the organiser of Calgary's No Pants Skytrain Ride. "There's no real reason, just come out and play."

In Sydney, dozens of local pranksters converged on St James Station in the CBD, simultaneously exposed their undies and hopped on a train

The premise is simple: don't wear pants, ride the set route, and keep a straight face. But there are rules, such as being "tasteful and hygienic", wearing "everyday" clothes from the waist up, and carrying a valid ticket.

"If questioned, you do not know any of the other pants-less riders. Tell folks that you 'forgot to wear pants'," organisers said on Facebook ahead of the Sydney event.

"Don't wear a thong or anything else that might offend people. Our aim is to make people laugh, not piss them off."

In Melbourne, the stunt went off without a hitch along tram route one, while on the Gold Coast, the privately-owned tram operator G:link shut it down just seconds before it was about to begin.