Feathers will fly this Saturday, 2 April, as citizens of the world take up down-filled arms to celebrate International Pillow Fight Day.

With events organised from Caracas to Cincinnati, these flash-mob style fights have been held worldwide since 2008, with more than 100 cities joining in the fun this year.

The light-hearted pillow fights, which the website says were initiated by the decentralised "urban playground movement", aim to turn cities into "urban living rooms" where public spaces can be reclaimed for social and spontaneous use.

The New York City event, with 5,000 participants, was the world's largest last year, and the Facebook pages of other organising cities currently show hundreds and even thousands of attendees. While the basics of the fight are consistent from city to city, some cities add their own flair, whether by asking participants to wear pyjamas (like London) or rush in at the designated time screaming "PILLOW FIGHT!" (in Vancouver).

To keep any of the events from getting out of hand, most organisers set a few ground rules on their events page, such as: "Don't hit people with cameras or people without pillows" and "Swing lightly". Some of the larger events ask fighters to bring non-feather pillows to mitigate the mess.

The fighting starts when a signal such as an air horn or whistle blows, and can last anywhere from a few minutes to a few hours. Once everyone is tired out, organisers like Newmindspace in New York collect pillows to donate to no-kill animal shelters and remind participants to clean up any mess.

Want to participate in the pillow-flinging action? Check out pillowfightday.com to find your city, or sign up to host your own.