Munchlax is one of the few baby stage pokemon. Other baby stage pokemon are Pichu, Igglybuff, Clefa, Tyrogue, Smoochum, Elekid, Magby, and Azurill. In the movie, it eats food at the city that the movie is set.
During the movie, it evolves into a Snorelax. Also, it evolved as block-robots cover it up, and Ash crossing it to get to a steel frame to show his passport to the main block-robot.