I bought a cat bed, a special self-heating cat bed (it has a layer of mylar inside). I was afraid they wouldn’t use it and it would be a waste of money but here (the grey one is Buddy – you can see from this shot why I frequently say to him, “Who is my great big bear of kitty? Who is the biggest kitty of all time?? Buddy!”):
The pattern clashes with the rug, but I have since tried the other side, which is all black, and they sleep on that side, too.