People all over the globe have used their weekends to attack one another - with feathers.
The project says over 130 cities participated in these mass pillow fights as part of International Pillow Fight Day.
In London's Trafalgar Square, people came dressed in pajamas, dressing gowns and fancy dress to take part in the good natured pillowfight Saturday afternoon. Most people carried feather-filled pillows that exploded as they fought.
London's Metropolitan Police said Sunday that the event had been peaceful and they had no reports of any trouble.
Organizers listed similar events in more than 130 cities around the world.
The fights were organized by The Urban Playground Movement which wants to encourage people to make use of public spaces.
The non-profit aims to have these events become a staple "of popular culture, partially replacing passive, non-social, branded consumption experiences like watching television, and consciously rejecting the blight on our cities caused by the endless creep of advertising into public space."
Take a look at the massive pillow fight in Barcelona, Spain below.
The Associated Press contributed to this report.