New Yorkers strip for the 11th annual No Pants subway ride

Who needs pants anyway? Clearly thousands were asking that question on Sunday.

The males of New York City got the chance to show if they are boxer and Y-front guys on Sunday in the annual No Pants Subway Ride event.

Straphangers throughout the city stripped to their underwear as part of a worldwide practical joke organised by prankster group Improv Everywhere.

Act like normal: A trio of girls make the most of the occasion by stripping down to their underwear

It was the 11th annual ride and, according to the group's website, all you had to do to take part was 'be willing to take pants off on subway' and 'be able to keep a straight face about it.'

Participants are asked just to act like they would on any other subway by chatting to each other, using their iPod or reading.

The event was not confined to NYC, cities including London, Washington and Mexico City also took part. 

In London the event was called the No Trousers Tube Ride, where about 150 people divided into groups for the various lines on the underground.

In Toronto they did for the fifth year running, with many people dressing up in fancy costume.

In Madrid it would appear the police and security weren't in on the joke. The No Pants brigade reportedly had to change their starting point when police prevented them from entering their original starting station.

Improv Everywhere was bo in 2001 in New York. 

The idea was to put together groups to pull off pranks and get laughs.

This year the group invited people to take part through Facebook, with more than 6,300 people accepting, the New York Daily News reports

A girl shows off her Superman tattoo as she lets her feet breathe by taking her boots off

Lone rider: Being on her own doesn't seem to bother this No Pants person

Bit of a quiz: Tourists and No Pants participants are squashed in together while two men show off their skimpy pink Y-fronts

A girl reads a book while a man walks past showing off his excellent colour coordination

Legs everywhere: At least Sunday's weather in New York was a respectable 45 degrees

Eyes straight: A fully-clothed passenger does a job ignoring a woman in her underwear just inches from his face

Less than impressed: A passenger has a look of indifference as he observes this participant's legs

Inteational affair: In London, a man maintains his stiff upper lip while in Toronto, right, the occasion appeared to have a more fancy dress flavour

Travelling light: In Mexico City, a man went out wearing just a necklace, underpants and boots while others try to ignore him

In Madrid a woman, presumably unaware of the event, took off her jeans mid-jouey to join in the fun