So my girls have had their cardboard box for about 6-7 months now...Maybe more, I don't exactly keep track but I know it's been at least that long.
It started off as a nice, perfect to sleep/stash food box.
A few months into box's life, my girls decided it needed a window:

Another couple of months went by...And at some point last night one of my girls did this:

Notice the perfectly horizontal chew pattern (ok i compromised it a bit with part of the roof collapsing during removal process)
I say it takes some talent to chew in such an angle and keep it horizontal. I think she might have been trying to demolish/remove one wall of the box for that 'open' feel/look.