Bowser Jr.'s Robot Reactor

"Wahahaha! You made it! But I won't even need my dad's help to take care of you!"

- Bowser Jr.

Bowser Jr.'s Robot Reactor is Bowser Jr.'s first galaxy in the game Super Mario Galaxy. In it, Mario fights Megaleg to earn a Grand Star.

This is a very small planet. Mario is required to entice a Bullet Bill to follow him and break open a cage to reveal a Launch Star, and then use that Launch Star to reach the Robot Reactor. This metal planet has a Black Hole that Mario needs to avoid. There are also other cages that can be broken to reveal coins or a 1-Up Mushroom. It is also infested with several Goombeetles and regular Goombas, which make it slightly harder to traverse the narrow pathways while being pursued by a Bullet Bill. There is an odd shortcut on this planet. If the player Triple Jumps off the cage with the Launch Star and Spin they can reach Megaleg faster.

This is where Megaleg is found and battled. It is fairly small and orange-brown, with many technologic symbols all over it. It has small rectangular areas on it that are transparent and seem to have computer components inside them. Despite Megaleg's probable immense weight, the transparent panels never break if Megaleg stomps on them, all that happens is a cloud of dust rises up. In the underside, there are several glass containers around the back of the planet that can be destroyed with the help of Bullet Bills for items. It orbits the starting Planet.

Megaleg's Moon
To defeat Megaleg and win this level, Mario must begin on the Starting Planet. There are three cages on the planet which must be hit by Bullet Bills and a couple of Astro Goombas. Mario must get a Bullet Bill to the third cage which contains a Launch Star leading to the Robot Reactor. On the Robot Reactor is where Megaleg is actually battled. Mario starts on the ground and Megaleg blasts Bullet Bills and tries to step on him to defeat him. There are multiple cages on the other side of the planet that a Bullet Bill can break open. If Mario runs up Megaleg's leg when it's on the ground, he will reach an area where three Bullet Bills are blasted at once. After dodging those Bullet Bills he must then move on to a turning gear area where he must hop the gears. Finally, he will reach Megaleg's head where there will be a cage and a Bullet Bill launcher. Mario must destroy the cage to open up another regenerative cage which he must destroy and a third cage in the middle of that one. Once Mario destroys all the cages, Megaleg will explode and Mario will fall to the ground with the Grand Star.
 * Enemies
 * Goombeetles
 * Bullet Bills
 * Megaleg (Boss)
 * Planets Visited
 * Starting Planet
 * Robot Reactor


 * Names in Other Languages

Super Mario Galaxy Trading Card Description
''Something very important is at stake in the battle against Megaleg, a giant cannon battery with mechanical legs that lives on its own Moon in Bowser Jr.'s Robot Reactor. Defeating this boss requires Mario to coax Megaleg into fireing its own Bullet Bills at itself.''

Trivia

 * If the player goes to the top of Megaleg and use the first person view to look at the starting planet, the player will see that it looks like its beta appearance, instead of being metallic.
 * Around the square panel on the base of the Tech planet where the glass cages are, the so-called technological symbols are S-Block Tetriminoes in different orientations. This is a reference to Tetris, which is another game franchise owned by Nintendo.
 * If players go to the back leg, they find a 1-Up.
 * After players beat the galaxy, the map icon for the galaxy turns into Megaleg.