I think they are actually using the doggie as a naturally warmed up fluffy mattress . You can see there is snow around, even under the doggie and the cats won't have any of that - not unless they have such a comfy, loving doggie as a cushion.
I am glad you enjoyed them too - they are heart warming
They are all adorable, but my favourite one is the second one as well. I just love the one on the right. The eyes and shape of the face are absolutely precious. I do believe I can detect of bit of "devil" in those eyes as well.