Wearing tutus, gorilla suits and pajamas, they came by car, bike and train to Cesar Chavez Plaza for a "flashmob" gathering Sunday that soon had adults behaving like children and filling the air with feathers, the San Jose Mercury News reported.
"This is building community through fun," said Bill Hoffman, 38, of Cupertino, "and bashing the heck out of each other and not getting mad."
Justin Triano, part of the "Bike Party" group that hosts bike rides in costume, owned up to initiating the gathering, saying it was time to add another fun event to downtown San Jose.
"We work hard Monday through Friday," Triano, a 27-year-old pharmaceutical sales account manager said during a break in the feather-fest. "We really want to have fun."
As participants pummeled each other with pillows, police and park rangers watched from the sidelines.
"They are an amazingly energetic group. I think some are reloading. I see some fresh pillows going in," park ranger Pam Helmke said. "We just want to make sure they don't damage anything or get hurt."