My Brother is a Superhero

Luke is a comic-mad eleven-year-old who shares a treehouse with his geeky older brother, Zach. Luke's only mistake is to need a wee right at the wrong moment. While he's gone an alien gives his undeserving, never-read-a-comic-in-his-life brother superpowers, then tells him to save the universe. Luke is massively annoyed about this, but when Zach is kidnapped by his arch-nemesis, Luke and his friends only have five days to find him and save the world...