Based on the the Cartoon Network show, Pet Alien: An Intergalactic Puzzlepalooza has you controlling five different aliens and managing their unique abilities over 80 levels to save their human friend, Tommy Cadle. The game received mediocre scores when it first hit stores last August, but a couple publications reviewed the Shin'en-developed puzzler favorably (Nintendo Power gave it an 8.0 out of 10).
GameStop currently has Pet Alien on sale at its online shop for $9.99, and they'll even ship it for free if you put in "SAVER" as a coupon code. Priced that low, this might be worth trying out. Even if cartoon-licensed games aren't your thing, this seems like a great, cheap gift for a younger sibling/kid/brat. Head past the post break for Pet Alien's trailer.