What's big and yellow and has really scary teeth?

On the chairlift at Copper Mountain, we kept riding above this thing. Finally skied down to check it out. Best we can figure, this snow cat was fitted with a special auger to help shape the half-pipes that dot the ski mountain. Snowboarders ride the half-pipes and do tricks. The blade on this had an incredible spiral. I included a shot of the entire machine to put it all into perspective.