Please don't be surprised if you find the passenger beside you only wearing shorts as hundreds of New Yorkers have been taking the metro subway trains in their underwear.

People take part in the 9th Annual No Pants Subway Ride in New York City January 10, 2010. The event organised by Improv Eveywhere involves participants who strip down to their underwear as they go about their normal routine.[Xinhua/Reuters Photo]

On Sunday, they stripped down to their undies for the ninth annual No Pants Subway Ride.

Participants gathered at six locations throughout the city. They were divided into groups and dispersed to different subway stations. Once inside the subway cars, they began calmly removing their pants and folding them up.

Most participants acted as usual straphangers: They read magazines or chatted with their companions.

The event started in 2002 with just seven people. It has spread to other cities.

The stunt is organized by Improv Everywhere, a group said to have a mission to cause "scenes of chaos and joy in public places."