Moon
- “When the moon hits your eye like a big pizza pie, that's amore!”
- —Mario's face, Mario Teaches Typing 2
The Moon is a celestial body that presumably orbits Mushroom World. If it is to be thought of as similar to Earth's moon, then it reflects light from the sun and so appears to glow at night.
In Super Mario Land 2: 6 Golden Coins, Mario is wearing a helmet when he goes to the moon (though admittedly he is traveling through space at the time), and in Paper Mario: The Thousand-Year Door Mario's partner Goombella states that there was no air to breathe on the moon, but since they were still alive and breathing, the Crystal Stars are suggested to have the power to supply air. Super Mario World 2: Yoshi's Island and Super Mario Galaxy both involved space-travel in which the characters didn't need helmets, but unlike Paper Mario: The Thousand-Year Door, no explanation was given.
History
Super Mario series
Super Mario World
The Moon's first appearance is in Super Mario World, where it made a very minor cameo in the background of the Star World map. In this cameo, the Moon was anthropomorphic in that it gave a smile and was shown to be in its crescent stage.
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 crescent stage, later appeared as a playable area in Super Mario Land 2: 6 Golden Coins, in which it was one half of Space Zone (actually two thirds if one counts the aforementioned secret stage). It was populated by many Cannon Pigs, and this was the first time any character ever explored it; when on the moon (and anywhere in the Space Zone) Mario was forced to become Space Mario, and the Moon had more gravitational affect on Space Mario than the star where Tatanga was fought did.
Super Mario 64
In Super Mario 64 and Super Mario 64 DS, The Moon can be seen in the background outside the mansion of Big Boo's Haunt.
Super Mario Galaxy
In Super Mario Galaxy, six "moons" are shown orbiting the Mushroom World. There are two green moons, a brown moon with holes through it (possibly where the Spin-Dig Galaxy is located), a small white moon, a small green moon and a small dark red moon. The boss Kamella comes from the moon on the Deep Dark Galaxy the second time she is fought.
Super Mario Galaxy 2
In Super Mario Galaxy 2, the Moon doesn't actually appear, although a similar body serves as a planet in Boo Moon Galaxy. There are no enemies on it, but if Mario stands on it it'll balance and possibly make Mario fall. Mario must collect the Star Chips on it to progress.
The Super Mario Bros. Super Show!
The Super Mario Bros. Super Show! episode "Count Koopula" showed that, if a Koopa Troopa stared at the moon when it was full, they would make the horrific transformation into a Wereturtle.
Yoshi series
Super Mario World 2: Yoshi's Island
A much smaller Moon also appears in World 5-8 of Super Mario World 2: Yoshi's Island; Raphael the Raven was combated on the Moon (Generic Ravens also used Moon-like planetoids as their native turf). Due to the size of this Moon, though, it is assumed that it is different than the more-common one progressed in many screens; this small Moon was given artwork in Tetris Attack (where it never actually appeared in-game) in a panorama featuring Raphael trotting it once more. After Baby Bowser is defeated and returns to his normal size, Kamek takes him and flies to the Moon for some unknown reason. This Moon also strangely resembles a baseball due to its stitches. 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 Story
The Moon next appeared in Yoshi's Story, where it was seen in the background during the fight against Cloudjin. A cardboard moon with two eyes and a nose can also be seen in the background of some stages.
Mario Party series
The Moon appears in many Mario Party games. Twila, a character from Mario Party 6, could be considered the physical manifestation of the Moon. Crane Game from Mario Party and Mario Party 2 also takes place on the actual Moon.
Paper Mario series
The Moon was supposed to appear in the prototype Forever Forest in Paper Mario in the background, though when Forever Forest was changed to its current appearance, it was removed.
Paper Mario: The Thousand-Year Door
In Paper Mario: The Thousand-Year Door, Mario and his party had to go to the moon in order to obtain the Crystal Star, which was 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 the Giant Cannon in Fahr Outpost. Once landing on the Moon, Goombella will also mention how a Goomba landed on the Moon in '69, which is a reference to the Apollo 11 landing; the first manned landing on the real world's moon in 1969. The Moon in this game is shown to conatin no land features other than craters and rocks. The Moon also appears in the background of Twilight Town and it's surrounding areas, as well, and seems to always be up in the sky in that area.
Luigi's Mansion
The Moon was later given an appearance in Luigi's Mansion, where it appeared in the background of the Observatory. Luigi, in his quest to find Mario's Star and progress in the mansion, ended up blowing the Moon up with a Meteor Ghost shot from his Poltergust 3000, which quite conveniently created a path of debris leading to the Star he was looking for. Very oddly, after this, the Moon could still be seen from the outside rooms and managed to show up in other games. It is therefore likely that Luigi destroyed a fake moon.
Donkey Kong Country Returns
The Moon also appears at the end of Donkey Kong Country Returns. After defeating Tiki Tong the Kongs are blasted high in the sky and fall down to the moon. Donkey Kong uses his fist to punch the moon into the Mushroom World's atmosphere and slam the Tiki Statue in the Volcano.