Any box will do.

Tips, the largest of all our rescue cats, now weighs in at 14 lbs.

He is a Siamese hybrid. So it's amazing he's that big. He has no problem taking a nap where ever he pleases. The other cats don't bother him, except his smaller brother who is a feisty red tabby. Here he's found a nice little box with some clothes in it to make a comfy bed.