Mario Galaxy (マリオギャラクシー, Mario Galaxy) is a stage that appears in Super Smash Bros. for Wii U. It was officially confirmed on November 15, 2013, though one of the daily pics on the site teased it as much as two months prior. This stage is available as one of the stages in 8-Player Smash.
The characters fight on a small, grassy planet in deep space. The background features a few trees and a house on the ground and, except in 8-Player mode, several spaceships in the sky.
Due to the planet's small size, the stage has a noticeable curvature to it: the center of gravity is the center of the planet, so jumping or getting launched upwards from the edge will cause the character to move diagonally. Most projectiles are also affected by gravity and move according to the planet's curvature, with a few exceptions, notably Fox's Blaster and Robin's Thoron.
Two static soft platforms are present, one on the right and one, higher, at the left. The stage also features walk-off blast lines. Star bits may occasionally rain down on the stage, though this has no effect on the fight.
Mario Galaxy is banned from tournaments due to the stage having walk-off blast zones and unusual gravity which interferes with projectiles and movement.
The stage no longer curves, walk-off blast lines are removed and gravity works like in most other stages.
This stage is based on both Super Mario Galaxy games. In the games, Mario would navigate through galaxies by going from planet to planet, with each planet having its own gravitational pull, to reach the goal. The planet on which characters fight in this stage is based on the starting planet of Gateway Galaxy, the first galaxy in Super Mario Galaxy, albeit with some differences such as the addition of the pine trees in the background, the presence of only one house instead of two (the house is also designed differently), and the much larger size of the planet itself.
Worthy of note is that at the end of Super Mario Galaxy the universe is reborn so that elements from many galaxies visited during the game end up closer to one another (with Mario welcoming this new galaxy), so the stage may have also gotten some influence from that, given that in Super Mario Galaxy there is no place called "Mario Galaxy".
The ships in the background are: