They beat the cardboard out of one another in Brooklyn Sunday - and it wasn't pretty.
Combatants dressed like cartoon characters and knights in shining cardboard crossed tubes in Williamsburg's McCarren Park.
"No poking, no stabbing, no aiming for the head," instructed Ravin Pierre, 27, of the Seattle-based Cardboard Tube Fighting League.
Still, it wasn't exactly an epic of good sportsmanship.
Joe Conklin, 28, of the upper East Side, wore a Chiquita banana box - or, as he put it, an "Aztec/Samurai-inspired helmet" - to beat a knight and dragon to a pulp.
"My strategy was to let the two players focus on each other, then go in for cheap shots," he said.
Ninja turtle Jeremy Westphal, 29, of Bushwick, won a hard-fought match against Josh Hager, 29, of Massachusetts, who dressed as the villain Shredder.
"He knocked my helmet off," Westphal said. "That's when I went into a berserk-o rage."