Ghostly Galaxy

The Ghostly Galaxy is a galaxy in Super Mario Galaxy. Many elements of this area are of a haunted theme, and Mario can even find Boo Mushrooms that turn him into a Boo. This galaxy also has the first appearance of Luigi in the game.

Enemies

 * Boos
 * Pink Boos
 * Swoopers
 * Pumpkin Heads
 * Goombas
 * Bomb Boos
 * Chomp Heads
 * Cosmic Scuttle Bugs

Starting Planet
The first thing Mario does in this galaxy is board a Toad ship, which always leads to the starting planet. The starting planet has about 3 Swoopers and 3 Pumpkin Goombas. There is a spike that contains a Rainbow Star when Star Spinned that could be used for destroying the Chain Chomp Heads in the first mission. In the third mission, there are 3 Scuttle Bugs. Each mission has a different Launch Star to get to the planets. There is a big gap in the middle of the planet that contains a Black Hole.

Mansion Planet
The Mansion Planet is a planet that resembles Luigi's Mansion in this galaxy. It is visited only in the first and third missions, though the third mission only has part of the Mansion. In the first mission, when Mario (or Luigi) enters the Mansion, he will come face-to-face to his first Boo in the game, providing that the player has not decided to skip this galaxy and go to another Boo containing galaxy (i.e. Deep Dark Galaxy). The Boo can be exterminated with a ray of light that gets turned on by a switch near the door. Also, there are some boxes near the edges of the room. Some of them contains Toads that give Mario information, while others give him Coins and Star Bits. There are also some Bowser Statues near the Boxes.

There is a painting of a Boo on top of the stairs and when Mario goes near it, the Boo spouts out, and when it is defeated, a key appears. After the plumber enters the door, he is now faced the challenge of finding the 5 Star Chips that makes a Launch Star that goes to the upper floor of the mansion. While finding the Star Chips, some Pumpkin Heads are there to make life difficult for Mario. Once he is on the upper floor, ha can go left and finds some Coins to add to his collection. But while Mario is collecting the 2 coins, he astonishingly sees Luigi trapped in a prison (or if the player is using Luigi, his "twin" is what's trapped). To save Luigi, Mario goes to the right and collects the Key to unlock the door. Going through it, he finds 2 Boos that appear in front of him, he kills them by Star Spinning them into a ray of light. Further on is an unreadable sign in the Boo language. Distraught, the hero goes forward to meet a ? Coin, and the first Boo Mushroom in the game appears right in front of the hero's eyes. Mario can now read the sign which reveals to be a Jill Board who teaches him how to be a Boo. The plumber then goes through the bars while invisible, and enters another room. He then encounters a Boo, who seems to find Mario incredibly attractive and decides to persuit him. When the Boo touches Mario, he loses his Boo powers and his true human identity is revealed, infuriating the Boo. The plumber then has to defeat the ghost by turning it into the light. Mario then continues on to get another Boo Mushroom near the corner, and uses it to pass through the walls to rescue Luigi.

In the third mission, only the first part of the mansion (with the Bowser statues) is seen. Instead of a Boo painting however, it is a Bomb Boo. It is used to destroy the statues to get coins, or to destroy the statue in the fireplace to proceed onwards. There are also the same boxes from the first mission, which contain coins, Star Bits, or Toads. When Mario enters the fireplace he is automatically inside a Launch Star, and is sent away to his next mission.

Bone Pen PLANET
The Bone Pen Planet is a planet priror to the real Bone Pen. It is your typical planet: round and able to walk "upside down". There are some trees with faces that have star bits on thier branches. Also some  shells are girded along the ground which the plumber may Star Spin near to get some Star Bits. The Spooky Speedster is found here.

Bone Pen
While techinaclly not a planet, it is is worth mentioning. It is where you race the Spooky Speedster and collect 100 Purple Coins in under 1 minute also 60 seconds. The Bone Pen is basically made up of Pull Star and bones so the player does not get out of the boundaries. After a while, there is a cow skull that lifts one of its 6 horns to stop the love of Princess Peach. There are also meat to bounces Mario stopping him.

Luigi and the Haunted Mansion
At first, Mario starts off on the Toad Brigade's ship, but has to use a Launch Star to reach the pathway into the mansion. Pumpkin Goombas litter the pathway, so Mario must be careful. Boos are inside the mansion, but a switch activates a swinging beam of light, which Mario has to lure them into to defeat them and get the items they are guarding. One of the Boos has a key to get deeper into the mansion.

Soon, Star Chips can be collected to rebuild a Launch Star which will then be located in one of the windows where a black hole was before. Using the Launch Star, Mario is then launched into another part of the mansion, where Luigi is calling for help beyond an impassable window. Mario will have to find another way inside, where he discovers a new power-up, the Boo Mushroom. As Boo Mario, he needs to vanish to pass through the bars, but he must be careful as a beam of light which will make him lose the Boo Suit is in the next area. Mario needs to return to normal before he can speak with Luigi to get the Power Star.

A Very Spooky Sprint
In this level, Mario must blast to the edge of the galaxy and race the Spooky Speedster through an area that looks like the Bone Pen.

Beware of Bouldergeist
Mario is informed by a member of the Toad Brigade that Luigi has been kidnapped by "The monster that lives up ahead". Mario will have to find his way to a circular stone platform and then meets Bouldergeist, a ghost with the ability to control stone. Mario will have to defeat Bouldergeist with Bomb Boos. After taking an amount of damage it eventually explodes, leaving behind a Power Star.

Bouldergeist's Daredevil Run
Very similiar to Beware of Bouldergeist, however Mario starts on the boss planet with a health max. of 1. This mission, until completed, is only available while a Daredevil Comet is in orbit. It is a very hard star to get since there are many ways to get hurt.

Purple Coins in the Bone Pen
Mario starts off on a small planet with the "Bone Pen" in front of it. The Bone Pen features bones as walls, meaty bones as bumpers, spiky balls as obstacles, and Pull Stars for getting around. Thre are more than 100 Purple Coins, but only 100 have to be collected by the player before the Power Star appears in the center of the pen. This mission, until completed, is only available when a Purple Comet is in orbit, and has a one minute time limit.

Matter Splatter Mansion
A mission similar to the Matter Splatter Galaxy. While playing the level "A Very Spooky Sprint", the ring shaped planet containing pumpkin-headed Goombas also has two breakable stalagmites. One contains a Rainbow Star, and the other contains a Launch Star to the Matter Splatter Mansion (there is a sort of light around the one with the launch star). Platforms and rooms only exist when a sort of "Spot Light" comes over them. The Player will need to go through, getting keys, and unlocking doors to get through; eventually, there will be a Power Star behind one of the doors.

Trivia

 * In the level "Beware of Bouldergeist", a Toad at the beginning of the level said Bouldergeist kidnapped Luigi, although Luigi does not make an appearance in the level. It is assumed, however that Bouldergeist is the creature that brought Luigi to the Ghostly Galaxy, as seen it the first level,"Luigi and the Haunted Mansion".
 * The level "Luigi and the Haunted Mansion" is an obvious reference to Luigi's Mansion.
 * Strangely, when the player is Luigi, the trapped Luigi still shouts "Mario". This may have been something the developers missed.