That's the left-over pizza boxes from Lunch !  

I don't know, maybe its to stop them kicking their legs back and hitting Gary Stern in the groin as he walks past or something.
Maybe its a form of torture, listen to Metallica cranked up, and you aren't allowed to dance and u have to keep your feet flat on the ground.
Last person standing (boom boom), wins a pizza for lunch !  

Also, notice how both Stern Managers are down, hanging around the hot chick, and aren't even near any of the others.