That's a great idea! I've done that (turned out we had one I just had to cut the top off of), and I did end up letting him out of the carrier. Immediately he climbed right into the box... and flopped down to be petted. *headdesk* So, not sure how well that'll work as a litter box, but at least he likes it. And I put a towel in the box, since that's still his "safe place" where he can lay down.