S2, E12: Dr. Animo has broken out of jail, and has been tracking down Ben, intent on revenge. At the same time, Ben's broken off a piece of the Omnitrix, and as a result, has turned into weird alien combinations, i.e. StinkArms. When Animo gets a hold of this piece of the watch, he uses it to create a ray that will mutate the entire world, until our heroes stop him.