A friend of mine kept them as pets. I was there once and watched one eat a piece of spaghetti. It held the noodle with both paws, sitting on its hind legs, and took bites while feeding it into its mouth "hand over hand". I have never really forgotten that. There was something so deliberate and skilled about this. No dumb beast, this, face down in a pile of food. This was an intelligent, fastidious creature enjoying a pasta dinner.

Rats are pretty clever, they can respond to their names and follow simple verbal instructions.

Back when I was a student I used to keep a couple, and several local friends also had one or two. They make good pets - larger and less fragile than mice, smarter and more interactive than gerbils, and not at all prone to biting you randomly.

I've seen squirrels bait cats and other animals in a playful fashion, facing downwards on a tree doing the undulating tail thing. Maybe rats are smarter, but squirrels are pretty playful and charismatic.