Dumbest stuff on wheels

Dinner was all ready and I called upstairs to the kids that it was time to eat. They were so busy playing, that they did not hear me. I went upstairs and found the bedroom door shut. I opened the door and the kids looked up guiltily from a pile of pillows on the floor. I figured that they had been jumping off of the bed and into the pillows, but I asked anyways. Reese answered, "We were just playing dumbest stuff on wheels!"