It was generally accepted that the planet did not, in fact, have an ass.
This conclusion was a very reasonable one - so reasonable that no one really disagreed with it. The only exception to this was the Royal Canterlot Society of Nonsense1, which had taken up the duty of thinking up the most silly and implausible theories to try and get a chuckle or two out of Princess Celestia. Among their ideas were heliocentrism, the dreaded 'rainbow factory', and the existence of a planetary butt. It was to their eternal shame that a clock, even when thoroughly obliterated, was right twice a day.
The planet did, in fact, have an ass - or at the very least, an asshole. It lay deep within the Badlands, a gaping vent in the earth which spilled tainted mana like a bad case of dysentary.
It was, rather unsurprisingly, not terribly healthy to live near, as was evidenced by the miles and miles of desert wastes that surrounded it. Which is not to say that nothing lived there - just that almost everything that did would rather be anywhere else. Even the Changelings, which had developed complex underground cities and needed less water than a particularly small cactus, hated the Badlands. There were really only two exceptions to this rule; the first being the beasts and spirits formed from the dark magic, which found the whole place rather homey, and the second being a race of monkeys2, which called themselves 'Humans'.
This was especially strange since humans were, in many ways, the butt of a rather cruel joke. They were not natural born hunters, like the Griffons with their killer instincts and wicked talons, nor could they boast the strength and toughness of the Minotaurs. Even their magic was pitiful, since usable mana was about a rarity in the Badlands.
Instead, they survived with nothing but melanin, a lot of complaining, and adaptation. Food was scarce, so they learned to farm. They were ill suited for fighting, so they learned to make arms and armor. They were delicious, so they learned to run away. That sort of thing.
Their home, which had little to offer but an abundance of deadly predators and relentless heat, could not have tried harder to kill them. And yet, against all common sense, they thrived. Built a city, made art, invented alcohol, all that good stuff. They had holidays and festivals and really just about anything that gave an excuse to stay as intoxicated as possible for as long as possible. They were for the most part, actually pretty happy.
Ironically, this made them something of a glaring beacon for every would-be evil tyrant in the Badlands. There wasn't much else to terrorize and oppress, after all, just a race of parasitic bugs that were already doing a pretty good job of oppressing themselves. So for decades, some ex-slumbering titan or dark god would show up, off the previous one and take over. This continued until the biggest, baddest evil tyrant was found. By the end, almost all of the humans were dead, their city was in ruins, they were slaves to a morbidly obese dragon and with all their plucky farmhands3 dead there was nothing left to make beer with anymore.
In the end, those who survived found themselves with two hobbies; toiling in the gem mines for their new master, and complaining to the heavens.
They were rather surprised when the heavens answered.
--O--
In Neighponese culture, there was a concept called 'Chuunibyou'.
It was not an entirely unique idea. Most cultures understood that, as children went through puberty, they might enter some sort of rebellious phase. Commonly, this involves trying to seem cool or special, sometimes through the means of an altar ego with an edgy name or some sort of unique power. And, during this rebellious phase, they might get into heated arguments with, say, their older sisters.
No one would ever realize it, but Luna was a massive chuuni4. Which was why, when monkeys poured out into ruined streets to celebrate the fact that their city was now covered in the gory chunks of their previous tyrant, she did not introduce herself as "Princess Luna of Equestria", but as "Nightmare Moon, Queen of the Eternal Night and Master of Darkness"5. The monkeys, which were still insisting that they were called humans, were really very used to this sort of thing by now, although a bit hesitant that their newest evil overlord would try to annihilate them for celebrating, like the previous sixty two.
Luna partied for seven days and seven nights before she decided to return home to her sister. By that time she had appropriated twenty seven new titles, including "Dragon Slayer", "Supreme Empress" and "Super Sexy". The humans would eventually rebuild their city, although they would never be quite so happy - or so drunk - as they had once been. Luna went on being a rebllious, chuuni alicorn, with a very frustrated older sister.
Between trying to run Equestria, fight the unending tide of world threatening evils and prank her sister, Luna would eventually forget about the humans. They would not forget about her, though. Which is why, a thousand years after Nightmare Moon was sealed away by the Elements of Harmony, a city of monkeys living approximately three miles6 away from the planet's asshole freaked the fuck out.
Seeing your god disappear off the face of the moon does that to a civilization.
In fact, to say that the humans freaked the fuck out was something of an understatement. Entire vocabularies and units of measurement would need to be invented to describe exactly how freaked out they were. The description would be a very long one, easily a few hundred pages when rendered into a scientific essay. Suffice to say, there was something of a panic. There were a few people who kept calm, however, and so they decided to do something.
None of this knowledge would have helped Twilight Sparkle stay calm when, about a month after she moved to Ponyville, she was ambushed7 in the dead of night by an especially ugly monkey.
Author's Note
The Royal Canterlot Society of Nonsense was eventually disbanded after it was discovered that Princess Luna was a bit more... gullible than anyone had expected. Cloudsdale was still rebuilding.
It is perhaps unfair to call them monkeys. They would resemble a monkey only after it were shaved, stretched and beat around the face for an hour or two. Also, monkeys are not stupid enough to live in the Badlands. Still, it makes them really mad, so we'll keep calling them monkeys.
The plucky farmhand community - which was previously in charge of growing crops, some of which were to be turned to booze - kept finding ancestral weapons and sage old mentors and running off to their gruesome demises. It was quite devastating. Their population never really recovered.
"Nightmare Moon" made her first appearance in Luna's "friendfictions", often alongside the tag : Original Character, Do Not Steal.
This introduction was accompanied by a series of strange, arcane hand gestures that would eventually pass into religious rite. Over a thousand years later, Equestrian historians would wonder how humans had learned sentai salutes.
It was really five kilometers away, but the humans just couldn't be bothered to convert to metric system.
He had, in fact, knocked on the door, been let in by Spike and had a nice cup of tea with the young dragon, but there is a reason why Twilight is known for overreacting, and not, say, being a perfectly reasonable individual who definitely never ensorcelled an entire town with a stuffed animal.
