People take part in the 'No Pants Subway Ride' in Vienna, Austria, January 10, 2016. © Heinz-Peter Bader

One day a year subway riders across the world get rid of their trousers and skirts to show off their new knickers and have fun as part of the “No Pants Subway Ride” day.

What started as a mere joke back in 2002 in New York by the Improv Everywhere prank collective, has now turned into an annual flash mob that brings together some 25 countries around the world , including the UK, Germany, Romania, the Czech Republic and Russia.

lots more funny pictures of pantless people at RT