Boo Moon Galaxy

Boo Moon Galaxy is a galaxy in the game Super Mario Galaxy 2, located in World 5. The level is a haunted mansion-themed galaxy. The starting planet is completely pitch black and requires some patience to reach the Launch Star. Its name is a pun on the phrase "blue moon". The level also has poison that makes Mario or Luigi lose a life instantly. Snake Blocks are found throughout the level. This is the only galaxy to involve use of the Boo Mushroom. Common enemies include Octoboos and Boos.

There are no Prankster Comets for this galaxy until the Green Stars are unlocked.

Ghost Maze Planet
The Ghost Maze Planet is a dark maze with a spotlight on Mario. It is full of Boos that chase Mario and try to harm him. This planet also has a Warp Pad leading to a Bonus Planet. The Launch Star is found at the end of this planet. This planet also has a Warp Pipe which leads into an underground tower and is only accessible after completing the first mission. There are some pictures of Boos and 1-Up Mushrooms in the walls. The doors that open when Mario approaches them make the same sound as the Super Mario World doors.

Petit Porter Planet B
Petit Porter Planet B can be accessible via the Teleporter on the first planet. It is inhabited by Jack O'Goombas. If Mario defeats all of them within the time limit, he gets three 1-Up Mushrooms.

Sinking Swamp
This planet has a series of Snake Blocks. If Mario steps on those, they start moving and Mario has to use them to progress, and if he falls back he falls into the poisonous swamp and dies instantly. These Blocks lead Mario into the Launch Star and a hidden star. Octoboos inhabit this planet and block Mario's path. A ? Coin present on the planet makes music notes appear which make three 1-Up Mushrooms appear if Mario collects all of them. A Comet Medal and a secret Power Star are also found on this planet. This planet is similar to a book, as it folds when Mario steps on certain platforms.

The planet is named in the mission The Star in the Sinking Swamp.

Crescent Seesaw Planet
The Crescent Seesaw Planet in this galaxy balances if Mario steps on it, and possibly make him fall into space when he stands on one of its sides too long. It acts like a see-saw. There are five yellow Star Chips on it that Mario needs to collect in order to form a Launch Star. This planet also appears in the ending credits of the game with a Red Luma, a Blue Luma and a Yellow Luma floating above it.

Rise Picture Book Planet
When Mario first lands on the Rise Picture Book Planet, he sees it is a giant book with grave drawings on it. But when he activates the switch, a wall raises revealing the three graves in 3D. Mario can jump on those to collect Silver Stars, Life Mushrooms and coins. The enemies encountered here are Boos. This planet is a pop-up book. When the player hits the ground pound switch a ticking noise plays and even when the pop-up book descends.

Howling Tower
A tall, sidescroller planet. This is the only place in the game where Mario can find the Boo Mushroom to turn into Boo Mario. The most common enemies here are Octoboos, who try to make Mario fall and lose his power-up. There are also fans in here. At the top of the tower is the Power Star.

This planet is named in the Haunting the Howling Tower mission.

Enemies

 * Boos
 * Octoboos
 * Jack O'Goombas
 * Spinecones

Green Star 1
The player has to do the same thing as the third mission, but, when they ride on the last series of the Snake Blocks, the Green Star is located to the left. They have to Long Jump with the right timing to grab it.
 * Enemies
 * Boos
 * Octoboos
 * Planets Visited
 * Starting Planet
 * Sinking Swamp

Green Star 2
This Green Star is located below the Moon. The player has to fall carefully to catch it. If the player misses the Green Star, they lose a life. They may need a spin to get it.
 * Enemies
 * Boos
 * Octoboos
 * Planets Visited
 * Starting Planet
 * Sinking Swamp
 * The Moon

Green Star 3
The last Green Star is located on the Graveyard Planet. To reach it, the player has to perform a Long Jump facing towards the screen from the graveyard's roof when it pops up.
 * Enemies
 * Boos
 * Octoboos
 * Planet Visited
 * Starting Planet
 * Sinking Swamp
 * The Moon
 * Graveyard Planet

Prima Official Game Guide description

 * "Once in a Boo Moon...this haunted galaxy is home to a whole host of Boos, so get ready to play a little hide-and-seek with these spectral foes. You also discover the Boo Mushroom here, though, so at least you can turn the tables when wearing the Boo Mushroom."