The sense is—'and he could romp about, exactly as if he were a puppy-dog.'
On horseback you think yourself somebody, but you look like a puppy-dog.
She shut her eyes, then like a puppy-dog snuggling to its mother, turned and dug her round little nose into the pillow.
He was lying on his back, with his paws in the air, and whining very like a puppy-dog.
If Pewee wants to put himself in as mean a crowd as yours, and be your puppy-dog to fight for you, let him come on.
