Prankster Comet

Prankster Comets are comets that appear in Super Mario Galaxy. They will appear from time to time in the orbits of the fifteen main galaxies, starting at the point when Mario or Luigi collect their thirteenth Power Star.

If the player travels to a galaxy when a Prankster Comet is in orbit, a special event will be triggered, which will usually change the gameplay of the level. Prankster Comets will only appear in galaxies after a specific Power Star in any given galaxy is collected. Also, when a Prankster Comet is in orbit, the player is forced to choose its level. No option is given to choose "normal" levels. However, there is a purple Luma near the Terrace who will shuffle the comets between available galaxies if fed twenty Star Bits.

By completing the event, the player will receive a Power Star. While a Prankster Comet is in orbit of a galaxy, players will need to completely restart the level each time they lose a life, instead of coming back at the last check point. Once a Prankster Comet's star has been collected, its star will become a selectable mission, only causing the comet to return to the corresponding galaxy at the player's request. All of the Prankster Comets also have their own music that plays during their missions.

Prankster Comet re-appears in Super Mario Galaxy 2. Here, Prankster Comets only appear once the player has collected a Comet Medal in certain galaxy, and has collected a certain number of other comet medals from other galaxies. There is a minor change - the comets are now yellow for Power Stars, while green for Green Power Star missions, which is only available after Mario collecting 120 Regular Power Stars and defeating Bowser in his Galaxy Generator once again. Galaxies under the influence of a Prankster Comet are given a generic symbol. This opens up the comet Star mission, although the player may have the option to select the mission, as opposed to the first game. As comet missions are no longer categorized by color clues, the next list names them in regards to the missions' titles.

There are five different types of Prankster Comets in the first game, each one a different color: red, white, blue, yellow or purple. These are also the known colors that Pikmin come in.

Speedy Comet
The Speedy Comet (レッドコメット Red Comet)  requires Mario to complete a level within a certain time limit, usually from 4 to 6 minutes. Also, there will be small changes in the galaxies. For example, Good Egg Galaxy's boulders are all replaced by Chomps; Space Junk Galaxy has several coins placed on planets; Dusty Dune Galaxy has none of its enemies except the five Pokey Sprouts, the Pokey and the boulders; Dreadnought Galaxy has one Spiked Topman where there was a Spring Topman. Four galaxies are visited by the Speedy Comet; the Good Egg Galaxy, Dusty Dune Galaxy, Space Junk Galaxy, and Dreadnought Galaxy. This comet also reappears in Super Mario Galaxy 2. An informal list of galaxies visited by it includes the Sky Station Galaxy, Bowser Jr.'s Fiery Flotilla, Bowser's Lava Lair, Rolling Masterpiece Galaxy, Supermassive Galaxy, Bowser's Gravity Gauntlet, Throwback Galaxy, Bowser's Galaxy Generator, the Stone Cyclone Galaxy, and the Boss Blitz Galaxy. An addition to some of these galaxies are Timers scattered throughout the mission; collecting one adds 10 seconds to the player's time limit.

Daredevil Comet
The Daredevil Comet (デスコメット Death Comet) sets Mario's max health to only one unit, as opposed to the usual three (or six with a Life Mushroom). Additionally, it removes all Life Shrooms from the level so that Mario cannot get them. Five galaxies are visited by the Daredevil Comet; the Battlerock Galaxy, Ghostly Galaxy, Gusty Garden Galaxy, Deep Dark Galaxy, and Melty Molten Galaxy. Four of them have the player fight a previously fought boss, with the sole exception being Melty Molten Galaxy, which has the player complete the entire first mission (The Sinking Lava Spire) with only one health unit.

Cosmic Comet
The Cosmic Comet (シャドウコメット Shadow Comet)  pits Mario in a race against Cosmic Mario in a predetermined course with a star at the end. Mario must beat his duplicate to the Star. Four galaxies are visited by the Cosmic Comet; the Honeyhive Galaxy, Freezeflame Galaxy, Gold Leaf Galaxy, and Sea Slide Galaxy. Hint: To get a head-start in front of Cosmic Mario, the player can hold forward on the Nunchuk, and when the timer reaches 2, press Z and Mario should turn yellow giving him an advantage. If the player is playing as Luigi, they will be racing against Cosmic Luigi instead. Unlike Cosmic Mario, Cosmic Luigi is more intelligent, and will take advantage of any shortcuts that are available.

Fast Foe Comet
The Fast-Foe Comet (クイックコメット Quick Comet) speeds up all enemies in a stage. Mario must complete the stage while avoiding the accelerated enemies. Only two galaxies are visited by the Fast-Foe Comet; the Beach Bowl Galaxy, and Toy Time Galaxy. Only Tox Boxes and Thwomps have been affected by this comet. The moving platforms also move faster. One familiar part is that it comes in galaxies with Tox Boxes,which are the Beach Bowl and Toy Time only.

Purple Comet
The Purple Comet (パープルコメット Purple Comet) is only available after the main story is beaten. Purple Coins are hidden throughout the galaxy, and Mario must retrieve one hundred, sometimes within a time limit, to retrieve the Star. Some Purple Comet missions have more than one hundred Coins, but Mario still only needs to collect one hundred for the Star. All fifteen "main" galaxies are visited by the Purple Comet. Timed Purple Comet missions, as well as the Battlerock and Dreadnought Galaxy's Purple Comet missions have unique background music, which some of it is a remix of the Gusty Garden Galaxy music.

Clone Comet
Multiple Cosmic Clones appears on a selected mission. The player needs to redo the whole or part of the mission while there are Cosmic Clones.

Romp Comet
Defeat a certain amount of enemies in a time limit, often with a power-up.

Green Comet
Makes some Green Stars appear in all levels, usually in hard to reach places.