Cats are all one size, but there are several dog sizes. If your dog is the size of a Chihuahua, meaning that you can put it in the palm of your hand, we call it a Small Dog. A Medium-sized Dog is a dog you can pick up, such as a Shih-Tzu. A Large Dog is one that’s too big to pick up from the floor, such as a Labrador. An Extra-large dog is one that little kids can almost ride like a pony, such as a Bernese Mountain Dog