Big dog on the couch, Kitty on the back of the couch.
Keep in mind that Kitty can go on a four mile run with me and be happy. He peters out after that, but still, four miles for a 20 pound dog ain't bad.
The big dog can run me into the ground. My legs could be worn down to nubs and he'd still be ready to go on. And then he wants to play fetch when we get home.