The music is absolutely captivating. Everything from the opening dance-hall sequence to the extraordinary use of the Kyrie from Mozart's Mass in C Minor during the storm at sea and the entrance into the harbor of Belleville. Notice how the music builds in richness as the camera descends from the few spires at the beginning of the sequence to the dense mass at street level.
Remembering the details and how they relate to each other and the film as a whole keeps you thinking about the significance of the film's contents. For instance, I only now remember that the opening sequence was drawn in the archaic, fluid style of early cartoon animation (Steamboat Willy, Olive Oyl and Popeye) because, of course, it was depicting events which predated the time of the film proper. The style served a purpose, beyond being an end in itself.
For a long time after watching the film I remained puzzled about its appeal to me. I've seen a large number of animated feature films, but none have left me quite as reflective as did this one. I was less concerned with the meaning of the details. It is a cartoon, after all.
I continued to wonder about Madame Souza's expression. About how the creator was able to invest such meaning in those simple dark circles set behind thick lenses and the line of her mouth, which modulated between forthright resolve and a gentle satisfaction. Then it occurred to me. Beyond the larger outline of the story and the details in which it is couched, it tells us of the power of one person's love and concern for another. I suppose we all wish we could receive such unconditional love, and it makes us feel warm to think that such a thing could actually be. Even if only in a cartoon.
The film either will or will not appeal to you, depending on what it is you're looking for in an animated feature film. I watched it without expectations, and was left wondering, "Why does it resonate with me?" And you'll want to see it again.