This is a pleasant film, even if the premise is silly. It was sort of a guilty pleasure to watch. Meg Ryan seems to be able to pull off roles in this kind of film (another example is Joe vs. the Volcano). That's what makes her a star, in part. Walter Matthau, of course, had that ability, too, and he really puts himself into the role, making an amusing, good-hearted Einstein. I suppose you could say they're both good at portraying loveable characters, though loveable in different ways (loveable young women vs. loveable curmudgeon).