Grand Finale Galaxy

The Grand Finale Galaxy is the final galaxy in Super Mario Galaxy. The galaxy is where Mario's home planet of Mushroom World resides. The galaxy is unlocked after all 120 stars are obtained with both Mario and Luigi, and is reached by talking to the fourth Green Luma on the Trial Planet. This galaxy has the 121st Power Star for both Mario and Luigi. The level takes place in Toad Town (also known as the Castle Gardens) from the beginning of the game, only there are creatures from other parts of the game are found there, including Penguins, Bees and Gearmos, the three major NPC types in the game. The Toad Brigade and their ship, the Starshroom, are found outside of the castle. After collecting all the Purple Coins, the Mailtoad will receive a message. If the player talks to him, he will send a congratulatory picture to the Wii message board. This picture differs depending on whether the player spoke to the Mailtoad with Mario or Luigi. The picture can also be sent to friends.

On the list of galaxies, it is simply called "Grand Finale", lacking the "Galaxy" name that all other galaxies use.

The Mushroom World
This is the main planet of the Galaxy and where most Mario games take place. Super Mario Galaxy only shows Toad Town and Princess Peach's Castle though. The castle and the area around it is based off its look in Super Mario 64. the area contains a large lake with a river flowing into it and a pathway to Toad Town. The path goes through Toad Town and into the castle. There is an invisible wall, like the ones found at the limits of the levels in Super Mario 64, that stops the player from entering the castle itself.

The Star Festival
The Star Festival is the only level of the Grand Finale Galaxy in Super Mario Galaxy. The mission requires the player to collect all 100 Purple Coins. After getting them the player receives the 121st Power Star. However, before collecting the star, the player may talk to the Mailtoad to receive a congratulatory message and attached picture, which is sent to the Wii Message Board. It is named after the event at the beginning of the game, which occurs every 100 years.

Trivia

 * Even if the big planet that is seen under most of the galaxies and even the Observatory is the Mushroom World, the Grand Finale Galaxy seems to be located too far from this planet to be it. Either this means that the planet that is always seen is not the Mushroom World, or this is an error from the creators of the game. It is also a possibility that Grand Finale Galaxy is a different galaxy parallel to the Mushroom Planet, but this is impossible because the Toad Brigade returns to this galaxy after their adventures during previous galaxies (revealed during dialogue with the Toad Brigade and other Toads in the Grand Finale Galaxy) and can be actively encountered, which means this is obviously the place where they came from and thus the Mushroom Kingdom.
 * Although Peach's Castle is in the area explored, there is an invisible barrier blocking entry to the castle, possibly because the Peach's Castle area has not been designed and thus it is closed off from the player.
 * The area outside the castle is very similar to the area outside the castle in Super Mario 64, except that various trees, signs, areas and the hedge maze have been removed and there is now a path to Toad Town.
 * In Super Mario Galaxy 2, it is revealed that everyone's memories of the prequel were reset (save possibly Mario and Rosalina). Therefore, either the events of this galaxy take place after the sequel, or it is some kind of parallel universe (not unlikely, judging from "Super Luigi Galaxy").