The feathers (and polyester filling) were flying at Washington Square Park on Saturday afternoon at the 10th Annual International Pillow Fight Day. It began at 3 p.m. and went on for hours…and hours. People would leave — arms worn out, faces battered from combat — only to be replaced by scores more who joined the fray. There were children, teens and parents, some in pajamas. One man, after giving it his all, dropped to the ground in utter exhaustion, top, where, lying amid clumps of torn polyfill, he got a kiss of concern from a pint-sized pillow warrior. It was silly, for sure, but a welcome relief from months of cabin fever. Of course, a drone was on hand to film it all.