My cats love boxes, especially for napping. If I put a box out for them to play in, they just turn it into a den for sleeping or sitting . When there is just one box it soon becomes obvious that there is lots of competition of who will dive into the box when one of them vacates the special place. I have watched the competion to see which cat will be the next one. Often two cats that have been waiting for a turn ,will begin swatting/slapping each other for that precious box.