Wobbly Robot: This was an upgraded form created by Lakitu to make Minor Robot work faster. It went haywire, so Luigi defeated it. It was thrown into the junkyard, later becoming Scrapped Robot. Wobbly Robots are also individual enemies from Mother 3.
Scrapped Robot: Scrapped Robot is Wobbly Robot after he was scrapped. He journied back home, learning that friendship matters to it. It was then up-graded to Upgraded Robot. Scrapped Robots are individual enemies from Mother 3. They are just like Wobbly Robot in appearance, except it is beat up.
Upgraded Robot: The last and current form of Minor Robot. He is now very fast and never makes mistakes with chores given by Lakitu.