Bowser Jr.'s Lava Reactor

Bowser Jr.'s Lava Reactor is a galaxy in Super Mario Galaxy. This is where Mario battles King Kaliente once again and receives a Grand Star. The galaxy is one extremely large planet made completely out of lava with very few rocks.

Starting Planet
This is a small dirt planet that is being eaten away by its black hole center. It is home to several goombas and has a bullet bill blaster to keep away intruders. There are three cages with various items including a 1-up mushroom, several coins, and a launch star.

Lava Reactor
This is a very large lava planet with two small solid platforms and several metal. Mario fights King Kaliente for the second time.

King Kaliente's Spicy Return
Upon entering the galaxy, Mario will land on a small planet with a few Goombas, a Bullet Bill Blaster, and a caged Launch Star. Mario will have to lure a Bullet Bill to the cage to smash it open, gaining access to the Launch Star. The Launch Star will shoot Mario to the Lava Reactor's surface, which is entirely lava, except for a few platforms sinking platforms. There, Mario will encounter two brown Cosmic Bloopers that he will have to defeat to access another Launch Star. From there, Mario will encounter Bowser Jr., who will make him fight a much stronger version of King Kaliente. Upon defeating King Kaliente for the second time, Mario will receive the sixth Grand Star.

Trivia

 * There is a glitch here. In the first planet, the player has to make a triple jump while playing as Luigi and land the second jump on top of a cage. Then the player has to Star Spin in middle of the third jump and, if done correctly, the Lava Planet's gravity will attract Luigi and he will lose a stock after falling in the lava.

Enemies

 * Goombas
 * Bullet Bills
 * Electrogoombas
 * Lava Bouncers