Hey, it's Nozomi Ohashi, that girl who sings the Ponyo song! And she's wearing some sort of tutu, sitting in some sort of abstract white environment and playing New Super Mario Bros. Wii.
That's how Nintendo is selling the game in Japan — roping in Japanese celebrities to play the game. Not the most exciting ads, but they'll probably do the trick. Oh, and here's the Ponyo music video!