Pillows fly near before the Elizabeth Bridge on the Danube in Budapest, Hungary, on Saturday, International Pillow Fight Day.
Janos Marjai/EPA via Landov
In London, the pillow fight was in Trafalgar Square.
Olivia Harris/Reuters via Landov
In Hong Kong, they fought with pillows a week early.
Jerome Favre/EPA via Landov
Germans fought in front of the Brandenburg Gate in Berlin.
After the fight, German municipal workers had to clean up the feathers.
Thomas Peter/Reuters via Landov
In Shanghai last Saturday, police broke up the fight.
Carlos Barria/Reuters via Landov
And in Taiwan, International Pillow Fight Day apparently had a sponsor.
Shengfa Lin/Reuters via Landov
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If it's not already marked on your calendar, here's your warning: Today is International Pillow Fight Day. Cities around the world are taking the holiday seriously — as serious as a pillow fight can be, anyway.
Organized through Facebook and other forms of social media, the flashmob fights are often surprises for an unsuspecting public caught on a field of sudden battle. In Shanghai, as MSNBC.com reports, the cushy conflict was hastily broken up by police after just five minutes.
If you are unfamiliar or unprepared, don't worry; Pillowfightday.com has a handy guide plus a list of cities that are participating. "Never ask permission" is one of the tips the site offers.