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, Gearmos, and Star Bunnies, 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
If you were looking for the event also called the Star Festival, see here. 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

 * Although Peach's Castle is present, there is an invisible wall blocking the entry of the castle, possibly because the Peach's Castle area has not been designed and thus it is closed off from the player.
 * Contrary to popular belief, it is possible to die in this level. It can be done by jumping into the fire roasting food just past the gate to Peach's castle area.