My cats LOVE boxes or absolutely anything else they can get into! We have a Kitchen-Aid box from my stand mixer that has sat in our family room for MONTHS now because the cats love to sleep in it. Yes, we are ruled by our cats...it's sad.
One of our cats has NO depth perception despite having tons of whiskers and antennae - he has tried to fit into a Kleenex box before...a Hot Pockets box...and TONS of other things - truly amazing to watch him get himself out of these predicaments every time.
What do they say about cats? 'Dogs have owners and cats have staff!' - that's our house...