If you were somewhat baffled by the greater than usual number of trouser-less riders on the Metro in Paris on Sunday, here are some videos to show what it was all about.
It was all part of an event called the 'No Pants Subway Ride' that started in New York City back in 2002 and has since gone global. The only rules are to act normal, not laugh and not wear trousers. If you can do all three, then you are perfectly eligible to take part.
It's intended to be fun for you and the unsuspecting strangers who will be surrounded by pants-less riders. As you'll see in the video not everyone got the joke.
This video from French newspaper Le Parisien, shows a bit more skin and contains a string of French-language interviews from 'No Pants' riders.