Or Mrs. Mouse is the puppy that Harry didn't necessarily save.
Considering Harry's habit of trying to save Distressed Damsels, it would be quite amusing to watch him playing second chair to Mouse being the stubborn, headstrong, White Knight, rushing into danger to save a woman (dog). He would get to be an amusing hypocrite again, like he was when he first got Mouse, and commented about his puppy behaviour, even though he acted the same way.