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Passengers stripped off today in a cheeky international stunt for 'No Pants Day'.

Organised by US practical joke group Improv Everywhere there was a co-ordinated subway ride across New York City.

People were invited to take part in travelling without their trousers as long as they could keep a straight face - according to the official Facebook site.

And the craze even spread to London with a group of Arsenal fans pictured in just their underpants ahead of their game against Manchester City at the Emirates.

(Image: Twitter)

The stunt spread to Stockholm, Sydney and Shanghai as stunned tube, metro and subway users looked on, bemused.

It was the 12th annual bare-legged event.

Organisers gave the thousands of brave participants detailed instructions: "Sit in the [subway] car as you normally would. Read a magazine or whatever you would normally do.

"Your team leader will have already divided you into smaller groups, assigning your group a specific stop where you will depants.

"As soon as the doors shut at the stop before yours, stand up and take your pants off and put them in your backpack.

"If you’d like to use a briefcase, purse, grocery bag, or whatever instead of a backpack that’s fine too.

"If anyone asks you why you’ve removed your pants, tell them that they were “getting uncomfortable” (or something along those lines.)

"Exit the train at your assigned stop and stand on the platform, pantless. You will wait on the platform for the next train to arrive. Stay in the exact same place on the platform so you enter the next train in the same car as you exited the last train.

"When you enter, act as you normally would. You do not know any of the other pantless riders.

"If questioned, tell folks that you 'forgot to wear pants' and yes you are 'a little cold'. Insist that it is a coincidence that others also forgot their pants. Be nice and friendly and normal."

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Jokers were advised to wear "fun underwear" but nothing too radical or offensive like a thong.

Last year Improv Everywhere claimed 4,000 people took part in New York alone.

People took to Twitter across the globe to share pictures.