Saturday's events in about 150 communities were part of International Pillow Fight Day, promoted by the public art group Newmindspace, the Los Angeles Times reported Sunday.
"When you're a kid a pillow fight is the thing you'd do when your parents weren't around," said Francis Co, 25, of Whittier, Calif., one of those taking part in the fluffy fights in LA's Pershing Square.
Co, dressed in pajamas and a surgical mask to keep feathers out of his mouth, also wore eyeglasses without lenses for strategic reasons.
"People generally don't hit you as hard if you're wearing glasses," he said.
Phil Holland, 30, recommended patrolling the perimeter for maximum effect and self-preservation.
"If you want to hit a lot of people, stay on the rim," Holland told the Times, adding it was wise to stay out of the center of the action where fighters took the worst beatings and inhaled the most feathers.
Chris Salvador, 18, and two friends even brought couch cushions he called PMDs, or pillows of mass destruction.
"These are military-grade," Salvador said. "It's like Mike Tyson locked in a pillow. This ain't a joke. This is a war."
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