The Moon is a celestial body that orbits a planet (based on Planet Earth's natural satellite). It has made several appearances in Mario games, either as decoration for a background or as a setting for a particular level.
Super Mario series
Super Mario Land 2: 6 Golden Coins
The moon, also smiling (although its expression could be changed based on completion of a secret level) and in a waxing crescent phase, appears as a playable area in Super Mario Land 2: 6 Golden Coins, in which it is one half of Space Zone (actually two thirds if one counts the aforementioned secret stage). It is populated by many Bomubomus, and this was the first time any character ever explored it; when on the moon (and anywhere in the Space Zone) Mario is wearing a spacesuit, and the Moon has more gravitational affect on Mario than the star where Tatanga was fought did.
Super Mario Galaxy
Super Mario Galaxy 2
In Super Mario Galaxy 2, six moons are shown. There are two green moons, a brown moon with holes through it, a small white moon, a small green moon and a small dark red moon. A similar body serves as a planet in Boo Moon Galaxy. There are no enemies on it, but if Mario stands on it, it balances and possibly make Mario fall. Mario must collect the Star Chips on it to progress.
Super Mario Odyssey
In Super Mario Odyssey, the moon appears as the location of three kingdoms, being the Moon Kingdom, the Dark Side, and the Darker Side. The Broodals, recurring antagonists from this game, originate from here. The Moon's importance to the plot extends to the Power Moons Mario must collect in this game, as well as the fact that the Moon Kingdom was where Bowser intended to force Princess Peach to marry him. The Moon also appears in the backgrounds of all of the kingdoms, floating high up in the sky. While the Moon's maria look the same, unlike the Moon in real life, the Moon in the game is much larger (roughly about the size of either the planets Mars or Mercury), orbits much closer to the Earth, and its maria are located on its southern hemisphere instead of on the hemisphere facing Earth.
The Super Mario Bros. Super Show!
Mario's Time Machine
In the NES release of Mario's Time Machine, Bowser steals the American Flag from the Apollo 11 mission in 1969 to put in his museum. Mario must return the flag to the Apollo Lunar Module. In this stage, Koopa Troopas are given space helmets and the Bird is replaced with a UFO. This is the only area in the game where enemies go through cosmetic changes befitting the location. An unnamed astronaut also wanders in front of the lunar module.
Mario Kart series
In addition to appearing in the Mario Kart series as the setting for several race and battle courses, the moon also appears in the background of many courses set during the night, such as Moonview Highway in Mario Kart Wii.
Mario Kart: Super Circuit
The course Cheese Land seems to be on a Moon made out of cheese, due to the amount of Moon-like craters; it also has a moon in a starry sky. Little Mousers can be found here. The track returns in the DLC for Mario Kart 8 (as well as the base version of Mario Kart 8 Deluxe); however, it is no longer moon-themed, due to the daytime sky, as well as a more desert-like look and plateau-like layout.
Mario Kart 7
Mario Kart 8 Deluxe
The battle course Lunar Colony takes place on the Moon and once again features low gravity and craters that the player can trick off of.
Super Mario World 2: Yoshi's Island
A much smaller Moon also appears in Raphael The Raven's Castle, which is World 5-8 of Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. Raphael the Raven was combated on the Moon (Generic Ravens also used Moon-like planetoids as their native turf). Also never appearing in-game, an artwork released for Tetris Attack shows Raphael on the same Moon. In Super Mario World 2: Yoshi's Island, after Baby Bowser is defeated and returns to his normal size, Kamek takes him and flies to the Moon for some unknown reason. Super Mario World 2: Yoshi's Island's moon also appears in the background of the Yoshi's Island stage in Super Smash Bros. Brawl.
Yoshi's Woolly World / Poochy & Yoshi's Woolly World
Mario Party 8
Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, Mario and co. have to go to the moon in order to obtain the Crystal Star, which is located in the X-Naut Fortress. The X-Naut Fortress itself was located on the Moon, as well. The only way Mario could get to the Moon was to fire himself out of Grande Boom in Fahr Outpost. Once landing on the Moon, Goombella also mentions how a Goomba landed on the Moon in '69, which is a reference to the Apollo 11 landing (the first manned landing on the Earth's moon) in 1969. The Moon in this game is shown to contain no land features other than craters and rocks.
The Moon is also consistently visible throughout Twilight Town - it is an apparently significant object to the villagers there, who believe it has the power to grant wishes. One of the Twilighters even foreshadows the fact that Princess Peach is being held captive on the moon; if Mario speaks to him after his name and body are stolen, he exclaims that someone living on the moon must have heard his wish to not be turned into a Pig before asking Mario who he thinks lives there, to which there are two possible answers - "little green men" or "Princess Peach."
On the Moon, with its low gravity, Mario and co. jump much higher than normal but also move more slowly, making it difficult to avoid enemies such as Moon Clefts. The Moon spans six areas, which loop unlike other areas in the game. Interestingly, when approaching the X-Naut Fortress from the foreground, a high-pitched sound can be heard.
The in-game map description reads, "The best place in the world for stargazing, but also a place pocked with craters large and small. In contrast to the world where Mario and his friends live, it's very difficult to traverse."
A version of the Moon appears in Luigi's Mansion, in the background of the Observatory. Luigi, while progressing through the mansion, blows up the Moon up with a Shining Ghost shot from his Poltergust 3000, creating a path of debris that leads to the Star he is looking for.
Donkey Kong Country Returns
The Moon also appears in each of the possible but similar endings for Donkey Kong Country Returns, depending on the characters remaining. After defeating Tiki Tong, the Kongs are blasted high in the sky and fall down to the moon. If only Donkey Kong defeats Tiki Tong, Donkey Kong uses his fist to punch the moon into the atmosphere and slam into Tiki Tong Tower in the Volcano. If Tiki Tong is defeated by Diddy Kong, Diddy attempts to escape the gravitational pull of the Moon to no avail and lands on his head. However, the force of the impact also results in Diddy unintentionally causing the moon to fall and slam into the tower. If Tiki Tong is defeated while both Kongs are active, Donkey Kong has Diddy Kong speed him toward the moon with his jetpack, accelerating Donkey Kong as he punches the moon, which causes it to fall onto the tower. After the moon crushes Tiki Tong Tower, the volcano erupts the banana hoard, sending the moon back into its original position.
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