Hundreds of people in cities around the world stripped down to their underwear on public transport for the annual No Pants Subway Ride on Sunday.

The idea is for participants to maintain a normal air, chatting with fellow passengers, listening to music, reading newspapers, while keeping a straight face as if tall was perfectly normal.

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A man takes part in the annual No Pants Subway Ride in New York. Participants in the event strip down to their underwear as they go about their normal daily commute.Reuters
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Commuters in their underwear take part in the No Pants Subway Ride in New York, where the annual event began in 2002Reuters
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The flash mob results in bizarre scenes on the public transport systems of many cities around the world, including Berlin...Reuters
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...Mexico City...Reuters
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...Hong Kong...Reuters
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no pants chicago
no pants kiev
no pants prague
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...and BrusselsReuters
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Another photograph of the 2014 event in Mexico CityReuters
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Another photo from the No Pants event in BerlinReuters
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Passengers in their underwear wait for a train during the "No Pants Subway Ride" event at a Metro station in ParisReuters