And yes, that's a little guy with a fishing pole. He seems to have been out for a little night fishing. I don't think he caught anything. Probably because all the fish are in the sky.
Perhaps another reason I loved Ponyo so much: I've always thought of slightly anthropomorphized fish as being all happy and exuberant, just like in the movie.
I also like this painting because it's kind of in the style of children's books illustrations. I remember seeing an exhibit of illustrations from some award winning children's book in a museum in Washington D.C. and realizing that illustrations in children's books are often fine art with as much merit as the stuff hanging in museums. And in fact, I often find illustrations in children's books more compelling and accessible than stuff in you find in museums or art galleries.
Oh, and for those who are curious, the stars are indeed meant to imply the constellation Pisces.