Hard landing

The other day, Max and Stella were chasing each other around the kitchen.  I wasn't watching exactly what was going on, but I was listening.  It sounded like there was a mid-air collision and then someone fell to the ground, but it sounded strange.

This is what I found:

Apparently Stella fell into the box.  As you can see on the right, she was already trying to eat her way out by the time I took this picture.