I feel he doesn't give anything about himself being a mouse and Tom being a cat. He feels they are like 'two peas in a pod,' and simply wants to prove, from time to time, as to who is the boss.
he is the villain because he is smarter and more of a nerd. But Tom just wants too eat eat and eat the mouse so he does not use his brain that much. Well to be honest he does but his ideas are not smart and they can't work
