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.
There are rules, however, and WHYY's Newsworks site helpfully supplies some important ones:
Bring a soft pillow with a clean cover, sans feathers if possible.
No foreign objects in the cases: pillows only.
Be discrete prior to the event and keep all pillows secured.
Only hit others who also have a pillow.
Please, no beanbag chairs or body pillows.