How about switching up some cats and dogs? Peter would be a grey tabby dog, if such a dog breed could even exist. Pepper would just be a really fat cat that puts even Garfield to shame. Chuck however would get a change of breed as well as species. Is there such a thing as a feline German shepherd? Not really, however there is a German breed of cats called the German Rex, so that would probably be fitting for Chuck. He'll now work out by playing with balls of yarn and build up his arm muscles by shredding scratching posts, or whatever cats do for exercise.