Prankster Comet

Prankster Comets are celestial beings that occasionally descend upon a galaxy during the course of Super Mario Galaxy. While they are within the galaxy's orbit, a new challenge to obtain a Power Star will be presented; often a previous mission is used, but with an added criteria. Each of the main fifteen galaxies will present two comet challenges, one being specific to the level and the other being a Purple Comet. Their positions can be tracked on any of the maps found in the Comet Observatory.

While a Prankster Comet is in orbit, no other missions can be played on the galaxy in question. Prankster Comets will disappear if a Power Star is obtained from a different mission, and will reappear again if another is obtained. In addition, a Luma near the Terrace in the Comet Observatory will offer to move a comet for 20 Star Bits.

There are five kinds of Prankster Comets in total, as listed below:

Speedy Comet

The Speedy Comet is a red comet that challenges Mario to finish a previous mission within a time limit. If Mario runs out of time, he loses a life. Losing a life at any time during a Speedy Comet challenge will require Mario to start over from the beginning, despite any checkpoints he would have passed in the normal mission.

The galaxies that play host to the Speedy Comet are:

• Good Egg Galaxy - Dino Piranha Speed Run
• Space Junk Galaxy - Pull Star Speed Run
• Dusty Dune Galaxy - Sand Blast Speed Run
• Dreadnought Galaxy - Topman Tribe Speed Run

Cosmic Comet

The Cosmic Comet is a blue comet that triggers the creation of Cosmic Mario. Mario must race Cosmic Mario through a portion of the galaxy to reach a Power Star. If Cosmic Mario gets to the Power Star first, Mario will lose a life.

The galaxies that play host to the Cosmic Comet are:

• Honeyhive Galaxy - Honeyhive Cosmic Mario Race
• Freezeflame Galaxy - Frosty Cosmic Mario Race
• Gold Leaf Galaxy - Cosmic Mario Forest Race
• Sea Slide Galaxy - Underwater Cosmic Mario Race

Daredevil Comet

The Daredevil Comet is a silver comet that reduces Mario's health to one and challenges him to complete a mission without taking damage. It most often appears in conjunction with a boss fight, with the comet carrying Mario directly to the battle arena. The only exception is in the Melty Molten Galaxy, where Mario must complete the entire mission or be forced to restart from the beginning.

The galaxies that play host to the Daredevil Comet are:

• Battledome Galaxy - Topmaniac's Daredevil Run
• Ghostly Galaxy - Bouldergeist's Daredevil Run
• Gusty Garden Galaxy - Major Burrows's Daredevil Run
• Deep Dark Galaxy - Daredevil Run to the Ghost Ship
• Melty Molten Galaxy - Lava Spire Daredevil Run

Fast Foes Comet

The Fast Foes Comet is a yellow comet that causes enemies to travel faster in the galaxy where the comet passes by. In both instances of its passing, these enemies consist of Thwomps (regular and box-shaped) and spiked panels. Because Thwomps will instantly kill Mario if they crush him, these missions become somewhat more dangerous; however, Mario will always start close to the Power Star rather than at the beginning of the level.

The galaxies that play host to the Fast Foes Comet are:

• Beach Bowl Galaxy - Fast Foes on the Cyclone Stone
• Toy Time Galaxy - Fast Foes of Toy Time

Purple Comet

The Purple Comet is a special comet that appears after clearing Bowser's Galaxy Reactor. Unlike other Prankster Comets, it appears in all fifteen of the major galaxies. In all of these challenges, Mario must collect 100 Purple Coins without dying to make a Power Star appear. However, some galaxies have their own special conditions applied, including time limits or limited chances to get each coin.

The following galaxies have no special conditions, and only require Mario to collect every coin:

• Good Egg Galaxy - Purple Coin Omelet
• Honeyhive Galaxy - The Honeyhive's Purple Coins
• Beach Bowl Galaxy - Beachcombing for Purple Coins
• Freezeflame Galaxy - Purple Coins on the Summit
• Dusty Dune Galaxy - Purple Coins in the Desert
• Sea Slide Galaxy - Purple Coins by the Seaside
• Deep Dark Galaxy - Plunder the Purple Coins
• Melty Molten Galaxy - Red-Hot Purple Coins

The following galaxies employ a time limit during Purple Comet missions; most have 150 coins instead of 100, except for the Space Junk Galaxy and Gold Leaf Galaxy:

• Space Junk Galaxy - Purple Coin Spacewalk
• Ghostly Galaxy - Purple Coins in the Bone Pen
• Gusty Garden Galaxy - Purple Coins on the Puzzle Cube
• Gold Leaf Galaxy - Purple Coins in the Woods
• Toy Time Galaxy - Luigi's Purple Coins

The following galaxies will force Mario to ride a platform throughout the level, giving him only one chance to get every coin; if he misses any, the Gearmo at the end of the level criticizes his performance and takes a life:

• Battlerock Galaxy - Purple Coins on the Battlerock
• Dreadnought Galaxy - Battlestation's Purple Coins

In addition to these, the Gateway Galaxy offers a Purple Coin challenge as soon as it can be returned to, and does not require the Purple Comet to be in orbit. After meeting with Rosalina for the second time, a red Luma will appear and challenge Mario to collect 100 Purple Coins while using the Red Star power-up. If Mario does so, he earns a special red Power Star and the ability to use the Red Star in the Comet Observatory.