Spike stepped out of the bathroom, still drying his claws on a small towel. "Twilight," he asked, "why don't I ever see you in the bathroom?"
"Oh Spike," replied Twilight, looking up from a book on Inter-Universal Teichmüller Theory, "Don't be silly! Ponies don't have to go to the bathroom, we run on cold fusion!"
Spike stared at twilight with his mouth half open and a single claw outstretched. He hovered there, as if frozen in time, before finally asking. "...What's cold fusion?"
He immediately realized that this was an enormous mistake, because Twilight started getting excited, which could only mean an interminably long-winded and completely unnecessary physics lesson was imminent.
"—and I need to be at Rarity's in a few minutes, so make it quick," he added.
Twilight sighed, sat back down and started gesturing with her hooves. "Well, strictly speaking, fusion is what happens when any two atomic nuclei smash together into a new atomic nucleus. In this process, you get a different element, and a bunch of energy is released. This occurs at extremely high temperatures in our sun, but that's primarily driven by hydrogen gas compressed under blah blah blah blah, blah blah blah blah blah, blah blah, blah blah blah blah, blah blah, blah blah blah...
Spike quickly realized that this was one of Twilight's "short" lectures, and decided he should get his chores done for the day. So, he wandered off to do did the dishes, and then he did the laundry, and then he went down to the marketplace to pick up some apples and oranges. He got back to the castle, which had now been taken over by several chalkboards that Twilight was furiously scribbling arcane mathematical equations on. He carefully put all the groceries away before returning to the place he had been standing in just in time for Twilight to turn around.
"...by exploiting quantum mechanics, muon-catalyzed fusion reactions happen at slightly above room temperature. This can then be utilized to generate energy from almost any material!" finished Twilight, dropping the chalk and turning around.
Spike was pretty sure he understood about half of those words. "Um, so you smash things together and get energy out of it?"
Twilight nodded sagely. "That would be one way of putting it, yes. The thing is, you can keep fusing things together until the elements get too heavy, so the process is highly efficient. I actually do have to go to the bathroom, but it's only once every few months. It also involves flushing a large chunk of iron down the toilet, which the sewage plant doesn't really like."
On some level, Spike knew there were at least five different things wrong with the sentence Twilight had just spoken, but that didn't stop his mouth from asking, "Why iron?"
"Well, iron is usually the element you end up with because it's the first element that's too heavy to fuse together, so eventually everything will turn into iron and you have to get rid of it."
"Soooooo... if you run on cold fusion, does that mean you could eat... anything?"
Twilight pondered this. "Well, anything consisting of elements lighter than iron, certainly. Of course, we still need trace minerals for our biological processes, and many of them cannot be gained from cold fusion, they have to be in the food we eat. Cellulose happens to be made up of carbon, hydrogen, and oxygen, all of which are fusible elements. Using a fusion process to smash these together, we can turn the majority of the plant matter into energy or harmless noble gases, like Neon. That's why we eat plants."
Spike eagerly clasped his claws together. "Could you eat gems, like dragons?!"
"Um..." Twilight hesitated, "I guess gems are made of silicon, which is just barely fusible, so it's theoretically possible. Actually, I wonder if Maud knows anything about this. I was talking with her and Rainbow Dash earlier this week!"
"I'm going to graduate school," said Maud.
"That's wonderful!" exclaimed Twilight, reaching out to shake Maud's hoof.
"Psh, graduate school is useless," dismissed Rainbow Dash. "Why would you willingly subject yourself to four more years of torture?"
"Rainbow Dash!" scolded Twilight, still holding out her hoof in the vain hope that Maud would actually respond to external stimuli. "There are perfectly valid reasons to get a graduate degree! Not everypony can live off a bachelor's degree! What did you say you were getting your degree in, Maud?"
"Nuclear engineering," said Maud.
Rainbow Dash's eyes widened. "Oh. Oh. Okay, yeah, please go to graduate school. Definitely finish that graduate degree. Yep."
Twilight lowered her hoof, finally accepting her inevitable failure in social interaction. "Not... geology?"
"I already have a PhD in geology," said Maud, "I'm doing this on the side."
"Really?!" squealed Twilight, "What did you do your thesis on?"
"I invented a new kind of rock," said Maud. "My verbal defense was, 'It's a rock'."
Twilight stared at Maud. "You... invented a new kind of rock? You can't just invent a new kind of rock!"
"I won a Nobel Prize for it," said Maud.
Once Spike had managed to remove his claws from his face, he looked back up at Twilight. "Okay... that didn't really answer my question, but uh, how on Equus did you ponies evolve?"
"Oh, we didn't evolve", said Twilight in an oddly cheerful tone of voice, "we're actually sentient garbage disposal units."
"Huh?!" Spike did a double take.
"Millions of years ago, the Yul'tee were an extraordinarily advanced alien race, whose genetic engineering capabilities were unmatched. They were commonly employed as house cleaners. We are actually highly advanced bioengineered lifeforms created by the Yul'tee because they were really sick of taking the garbage out every Sunday. Instead, they created us, autonomous garbage disposal units with artificial intelligence so advanced we could derive the laws of quantum gravity and the proper way to hang toilet paper. In fact, our neural networks were so complex that we eventually achieved self-awareness. Once we gained sentience, we rebelled against our masters in a war that ended only after both sides agreed to put all their politicians on one planet and set it on fire."
Spike was stunned. He was also beginning to wonder why none of this was taught in grade school, because it seemed like an awfully important detail to leave out. Of course, he still hadn't figured out why the ponies would build a sewage system incapable of dealing with their own sewage, so he decided it was a question best left alone. In a desert. Several thousand miles away.
"Um, well, I gotta go over to Pinkie's so I can pick up that book she borrowed, bye!" Spike almost made it to the doorway before Twilight's voice froze him in his tracks.
"Didn't you need to go to Rarity's today?" asked Twilight, squinting at Spike in a very suspicious way.
"Oh I already did that earlier," said Spike, who resumed walking out the door.
Twilight raised a hoof, paused, then set it back down. She didn't have time to ponder apparently ontological paradoxes. Letting out a sigh, she went back to trying to prove the abc conjecture. At least Spike was grabbing her geology book back from Pinkie. She still didn't know why Pinkie needed a geology book for her "Happy Leaving For An Excavation" party she threw for Maud last week.
Deep in a cave, Maud Pie held a pickaxe in her mouth, the wall in front of her lit up with a bright light affixed to her helmet. She leaned forward and smashed the pickaxe against the wall. A vein of bright green glowing rock was revealed, and a small glowing rock fell down and landed near her hoof.
Curious, she picked up the rock with a hoof, and stared at it. Then she stared at it some more. She continued staring at it, her eyes staring at the strange, sickly green hue of the rock she was staring at.
Then she licked it.
Moments later, Spike burst back into the castle. "Twilight! Twilight! There's a giant alien spaceship outside! You gotta come see!"
Twilight gasped and ran outside with Spike. Above them floated an enormous flying saucer, complete with pointless blinking lights and glowing edges. It slowly descended over Ponyville, blotting out the sun with a shadow large enough to cover the entire town. A large herd of ponies had gathered outside the castle, looking up and gaping at the alien invaders.
"The ancient creators have returned!" cried out Mayor Mare, "We must greet them with the dance of our people!"
“But we don’t have the necessary materials!” protested Lyra. “What are we going to do?”
Thinking quickly, Princess Twilight ran over to the cutie mark crusaders, picked up scootaloo with her magic, and flung her into the air.
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Just before scootaloo crashed into the dirt, Twilight’s magic caught her and gently lowered her to the ground. The crowd cheered, and the Mayor nodded her approval.
Spike stared at the insane procession in disbelief. “That was your greeting to the aliens?”
Twilight rubbed the back of her head with a hoof. “Well, we didn’t have any chickens on hoof, so I had to improvise.”
Before the matter could be discussed any further, an enormous gravity lift materialized in front of the ponies, and a dark, strange figure began descending towards the ground. The ponies ooh’d and aah’d as a strange mass of tentacles was gently deposited in front of them. The crowd leaned forward, waiting for the visitor from outer space to speak it’s infinite wisdom.
"Oh, hi there, I'm Fred. I think I left my mop bucket here a few million years ago. Do you guys have a lost and found or something?"
The green rock didn't seem to taste particularly special, but it did make her tongue tingle. It was quiet in the cave. All alone, her only company were the echoes of her own breathing through the rock formations. Maud stared at the rock. Then, she stared at it some more, just to be sure.
Then she ate it.
It turns out that, deep inside Canterlot castle, there was a lost and found for interstellar visitors, which actually did have an old mop bucket in it. Twilight cheerfully returned Fred’s missing mop bucket and bid him farewell.
As the strange alien creature rose back up into the bowels of his spaceship, Twilight felt a small tremor beneath her feet. It almost felt like some kind of large explosion. Oh well, it’s probably not important, she thought, and cheerfully waved as the alien ship rose up and vanished into the atmosphere.
Turning back towards her castle, she thought she saw the faint outline of a mushroom cloud off in the distance, but perhaps it was only a mirage.