Book 1 in the Spaceheadz series.
From the Publisher: "Michael K. just started fifth grade at a new school. As if that wasn't hard enough, the kids he seems to have made friends with apparently aren't kids at all. They are aliens. Real aliens who have invaded our planet in the form of school children and a hamster. They have a mission to complete: to convince 3,400,001 kids to BE SPHDZ. But with a hamster as their leader, "kids" who talk like walking advertisements, and Michael K as their first convert, will the SPHDZ be able to keep their cover and pull off their assignment?"
Publisher: Simon & Schuster, 2010, 160 pp.