A Sunday in early January each year sees New Yorkers board the subway minus their pants -- and other cities across the world are following suit!

It's simple enough -- take the train. Don't take your lower garments.

This yearly Big Apple gag, which sees thousands of city dwellers ride the subway in their skivvies, goes back an amazing decade. Organised by comedy group 'Improv Everywhere', the annual New York No Pants Subway Ride started off in 2002 with just seven participants who rode the trains in their underpants despite the freezing winter temperatures.

Since then, the prank has seen more and more people getting into the spirit of things and the most recent ride on Sunday, January 8, 2012 saw an estimated 4,000 participants bare their legs.

Improv Everywhere claims that the ride is also taken by thousands more across the world in 59 cities and you can well believe them -- pantless pranksters have been spotted in London, Mexico and other world-famous metros.

Amid much giggling, pretending like nothing is out of the ordinary and snapping of pictures, participants board trains at each stop and then gather at designated stations; in the meantime, commuters who don't know of the gag respond with either amusement, shock or confusion. After all, everyone is wearing regular attire, from their coats and hats down to socks, shoes, even briefcases -- but no pants!

In the following pages, we bring you a few laugh-worthy pics from the No Pants Subway Ride 2012!

Considering the nippy weather, some participants are more daring than others! Here, a group of men take photographs as women stand about in lacy intimates.

Minus the clothes, it's business as usual -- a woman reads as she awaits her train, while another commuter is seen chatting on her cellphone.

Bright pairs of underwear brighten up the scene as people wait around a platform.

The majority of commuters at Union Square subway station seem to take the No Pants Subway Ride seriously!

It isn't just the New Yorkers who have a sense of humour -- seen here are pantless participants in Mexico City.

This is another still from Mexico, at Zocalo Square -- participants on their way to and from the nearby subway enjoy the sunshine and the sight of each other minus their garments!

Back in NY, a bystander looks on in amusement as participants wait to get on the subway.

A young boy is understandably confused as he looks up at a woman who's left half her outfit at home!

And of course, there are some eye-catching undies out there -- here at Union Square, a participant is only too happy to pause for a pic!