- "Go get them, Megaleg! Stomp them with the power of your Grand Star!"
- ― Bowser Jr. when Mario lands on the Robot Reactor.
The Megaleg is a giant robot in Bowser Jr.'s Robot Reactor in Super Mario Galaxy. He takes a part of his design from a Snifit. The game's second Grand Star is located in a chamber on the top of his head and is used to fuel his machinery.
This monstrosity is a humongous three-legged robot who can't fit entirely on the screen unless you get far away enough from his location. His moon is barely big enough to hold him. His head appears to be based off of a Snifit with glowing yellow eyes. Located on his legs and head are Bill Blasters. On his head is a chamber containing the Grand Star in it.
Megaleg makes his first appearance in the course intro of Bowser Jr.'s Robot Reactor during the intro where the camera pans from the Starting Planet to the reactor itself, which is located on Megaleg's Moon. After Mario makes his way to Megaleg's Moon, Bowser Jr. appears on his Airship to summon the Megaleg. He then tells the Megaleg to "stomp Mario with the power of your (his) Grand Star".
First Mario or Luigi must climb up the Megaleg's leg to get to his head, with several Bullet Bill launchers on it and rotating gears, then get one Bullet Bill (likely from one of the launchers on the boss's head) to hit the cage on top of his head. If they do not climb, he will continuously stomp on the Moon. When the Megaleg brings his leg down, Mario will die if he gets caught beneath the giant foot.
The second phase is the same as before, but more Bullet Bill cannons appear on the head, creating more chaos, and the dome is surrounded by a regenerating, rotating cage.
Alternatively, when the cage regrows, get a Bullet Bill to follow Mario or Luigi over the cage wall, and, thus, into the glass dome protecting the Grand Star. After it takes a second hit, it can no longer contain the energy, thus killing the Megaleg and scattering his pieces through space.
- Digga-Leg is a boss in Super Mario Galaxy 2 that appears to be based on Megaleg.
- Additionally, in a Nintendo Power interview, it was stated that Megaleg would return for Super Mario Galaxy 2. This was later proven false, with Digga-Leg appearing instead.
- Megaleg underwent several changes prior to the release of Super Mario Galaxy: he was originally encountered in the beta version of the Good Egg Galaxy, at which point there was nothing in his cage and his name was "Snifit Bot". The earliest beta version of Megaleg was known as "BossCrab", which had a different body design.
- The concept of climbing atop and moving on a large being was originally intended to be used in the final fight against Ganon in The Legend of Zelda: Ocarina of Time, though this was scrapped due to the fact that one would be unable to see Ganon while atop him. It was later reused in Super Mario Galaxy, much to the excitement of the development team.
- Megaleg's design and functions have some similarities to the original design of the Tripod Walkers from H.G. Wells' novel, "War of the Worlds", such as having searchlights for eyes and three legs.
- Most (if not all) of the other bosses in Super Mario Galaxy resemble another enemy in the game to some extent. Since Snifits don't appear in the game, Megaleg is the only boss that does not resemble another enemy in the same game. However, Digga-Leg from Super Mario Galaxy 2 looks almost identical to Megaleg, though it's different in size.