Thousands of people worldwide are shunning their pants for an annual event that began as a prank.

The “No Pants Subway Ride” is currently happening in all parts of the world, including New York, Washington, Los Angeles, Brussels, Amsterdam, Hong Kong, Delhi and Paris.

Improv Everywhere started the event in New York in 2002, the Washington Post reported, and describes itself as “a New York City-based prank collective that causes scenes of chaos and joy in public places.”

Organizers in Washington used Facebook to tell riders who want to join in to try to maintain a calm demeanor and act like riding the subway in your underwear is the most normal thing in the world.

Participants were reminded to bring pants with them in case anyone in authority orders them to put them on.

In Chicago, participates were reminded on Facebook to keep it modest and not be too revealing.

“Please make sure your underwear is not too revealing! All parts that may be deemed offensive MUST BE COVERED!” said the social media page.

Here’s the story behind the event:

Tweets abound with people excited about the event.

Getting my cute underwear on. No pants on subway Sunday starts in 40 mins

— Timothy (@Timothy_Fra) January 12, 2014

Happy No Pants Sunday

— Olive (@OliveHonecker) January 12, 2014

Waiting in line outside McGreevy's for the No Pants Boston Subway Ride post party….pant-less, of course. #NPSR pic.twitter.com/ssP3t4VLVJ

— BostonTweet (@BostonTweet) January 12, 2014

Here are a few videos from past years around the world.

Are you keeping your pants on today?

Image via Twitter