One Key Ring To Rule Them All
It was a terrible morning in Ponyville. Lightning struck trees and the rooves of buildings almost at random, giant hailstones caused great damage to homes and shops, and torrential rains created floods that carried away anything not nailed down. The day prior to this, Ponyville's buckball team had just beat Cloudsdale's in the Equestrian Cup by just one point, taking home this year's trophy.
Inside her magnificent crystal palace, Twilight Sparkle sat in her chair with a cup of tea and a book named How To Destroy A Continent (And Make It Look Like An Accident), completely ignoring the outside world that raged beyond her crystal walls. Spike sat next to her with a book of his own, a Power Ponies comic book named The Eternity Gauntlet #3 Suddenly, Twilight heard something knocking at her palace doors. She ignored it, being far too caught up in what she was reading to care about what was at the door. Then she heard it again...and again...and again.
"Should I get that for you, Twilight?" Spike asked.
"No no, I'll get it myself," Twilight stretched her hooves and flew over to her door, frowning all the while.
Twilight opened her door, expecting a package or something, only to find something truly odd indeed. On her doorstep, there was a large silver ring carrying an assortment of keys with a face in the center of it all. She could've sworn that it moved its gaze up to look at her. But that can't be right. Key rings don't look at ponies.
Right in front of this living key ring was a letter, freshly wet from the downpour, but still perfectly legible. Twilight picked up this letter, opened it, and began to read it:
Dear Twilight Sparkle,
I found this little guy while I was cleaning out my house, and I thought he would make the perfect gift for you. I know how much you love these kinds of creatures, after all. He keeps your keys safe and is fun to annoy people with. I hope you enjoy his company as much as I did.
Have a happy birthday!
-Dr. Ocsid
Twilight rolled her eyes. Of course Discord would be behind something like this. On top of that, it wasn't even anywhere near her birthday.
"Twilight, what is-" as soon as Spike caught sight of the key ring on the doorstep, he flinched and started to back away.
"Spike, what's wrong? Why are you acting so...skittish?" Twilight asked.
"I-it's nothing. Nothing at all," Spike attempted to compose himself, a few drops of sweat still lingering on his forehead. The key ring glared at him, and he backed further away, freshly startled.
"Well that doesn't sound like nothing," Twilight said. "What even is this?" When she tried to pick the key ring up to analyze it further, it writhed furiously in her magic in an attempt to regain control. When she let go, she found that it could float above the ground.
"Klefki!" the floating key ring said in a threatening tone.
Suddenly, all of the pieces fit in Twilight's mind, and she realized something. "This thing is a Pokemon!" Twilight exclaimed.
"A Poke-what now?" Spike said.
"I've seen them before! Hold on, let me get something!" Twilight ran off deeper into her castle, leaving Spike to fend for himself against the mighty beast. He stood completely still, sweating profusely, for the jingling of keys had terrified him into submission.
"Twilight, what is this?" Spike asked, pointing to a machine that looks like what you'd get if you glued a flat-screen TV to a dialysis machine that Twilight brought up from somewhere in her palace, with blinking lights ladled generously around the exterior and a lever to its side. The key ring floated above a chair on the machine's right side, hooked up to it via wires and jumper cables attached to its keys.
"It's my Pokemon Analysis Machine," Twilight answered. "I had it built when Pokemon attacked our world and nearly destroyed Equestria."
"Alright, that makes se-wait, what?!" Spike exclaimed. "These things attacked us?!"
"Yeah. It happened around...six months ago, I think?" Twilight said.
"You'd think I'd remember something like that," Spike said.
"Oh no, Celestia and Luna wiped everypony's minds of it after the fact, so nopony but them, us, and Discord know they exist," Twilight said. "Anyways, this analysis machine will tell us everything we need to know about this particular specimen!" Twilight pulled the lever on the machine's side, causing the blinking lights to blink faster and brighter than before.
On its massive screen, the analysis machine displayed as follows:
Name: Klefki
Sex: Male
Type: Steel/Fairy
Ability: Prankster
Weaknesses: Ground, Fire
Resistances: Normal, Flying, Rock, Bug, Grass, Psychic, Ice, Dark, Fairy
Immunities: Poison, Dragon
Moves: Thunder Wave/ Light Screen/ Swagger/ Dazzling Gleam
These key collectors threaten any attackers by fiercely jingling their keys at them.
"Immune to Dragon?" Twilight noticed. "Does that mean he's immune to any dragon's attacks?"
"Well that would certainly explain a lot," Spike said.
"So if I take Klefki into the Dragon Lands, he'll be completely untouchable!" Twilight said.
"Um, Twilight, I'm not sure that's how that works," Spike said.
Already a dark idea was beginning to form in Twilight's mind. "Oh, this is perfect! Once this bad weather clears up, those dragons will be sorry they ever opposed Princess Twilight Sparkle and her mighty set of keys!" She began to laugh maniacally, while Spike facepalmed in exasperation. This was going to be a long day...
Rainbow Dash slept peacefully in her bed of clouds. After all, it was noon on a Saturday, what else was she going to do? This blissful peace was shattered when an alarm clock materialized from thin air on her bedside table and immediately went off, ringing loud enough to wake the dead.
"Gah!" Rainbow sprang upright in her bed, smashing her new alarm clock into pieces. Once she calmed herself down with a few deep breaths, she looked over at Tank's bed on the far left side of her room. What she found instead of Tank was a small, turtle-like creature that was almost the exact same shade of light blue as her coat was, with a brown shell and a tail that was curly like a squirrel's. He was also wearing a propeller cap, just like Tank. This turtle creature began to stir, staring at Rainbow Dash with big, red-tinted eyes that somehow felt familiar.
"Squirtle squirt!" was all that this creature would say.
Rainbow Dash rubbed her eyes with her hooves, verifying that yes, this was in fact happening. She then turned around to her other wall to find a familiar draconequus staring back at her, filing his claws.
"Why hello there, Rainbow Dash," Discord said.
"Discord!" Rainbow Dash shouted. "What have you done to Tank?!"
"Do not be alarmed, my little Dashie," Discord said. "Tank is still mostly the same as he was before. However, now he's not just a turtle, but a Squirtle." Rainbow simply gave Discord a blank stare. "No? Not ringing a bell? Honestly, has everypony forgotten what a Pokemon is already? I remember you in particular gave a Tyranitar a good kick in the face while defending Twilight's castle."
"Look, will you just tell me what this is all about?" Rainbow asked.
"Why certainly!" Discord said, grabbing a pipe from nowhere and lighting it with his flaming thumb. "You see, while I was cleaning out my house, I found a living set of keys that I thought Princess Twilight would like. You know how she is with her weird collections and whatnot. So I sent him to her, thinking that she would enjoy him, when the next thing I knew, she was heading for the Dragon Lands with intent to take over with her invulnerable floating set of keys.
"So you're saying I have to stop her?" Rainbow asked.
"Well, yes." Discord said. "But there's also something else at stake. If you defeat Twilight in a Pokemon battle, you will gain the title of 'Pokemon Master'."
"Pokemon Master?" Rainbow Dash said. "That. Sounds. AWESOME! I wanna be the very best like nopony ever was!"
"Brilliant! Here, this book will probably help you. It is dangerous to go alone, after all," Discord dropped a large doorstopper of a book onto Rainbow Dash's bed. Emblazoned on the cover was a circle, with a red top half, a white bottom half, a black dividing line between them, and a smaller white circle in the middle.
"How To Battle Like A Champ (And Not Like A Chump) by Gary Oak?" Rainbow said.
"That's right!" Discord said. "Finest trainer in all of Kanto. He got ten badges when there are only eight gyms." Rainbow Dash stared at him like he was speaking gibberish. "Well alright then. Ooh, I also have something else for you!" Discord snapped his fingers and conjured a bicycle on the side of Rainbow Dash's bed.
"A bicycle? Really?" Rainbow asked disappointedly.
"Hey, it's better than walking," Discord said. "Well, I'd best be off now. Toodle-oo!" And with that, Discord vanished.
Rainbow Dash mounted her bike when suddenly she heard a voice in her head. Rainbow Dash! Now is not the time to use that!
"Princess Celestia?" Rainbow asked.
Yes, that's right, I'm talking to you. You can't ride your bike indoors, Celestia said.
"Watch me!" Rainbow Dash pedaled out of her house and off the edge of Cloudsdale, with the new-and-improved Tank following close behind.
"Klefki, use Thunder Wave!"
Ember suddenly found herself unable to move, her muscled seized up from the sudden burst of electromagnetic waves. She slumped with her back to the cave from which she ruled her domain, staring down the Princess of Friendship and her...floating set of keys? She had to admit, she did not see this coming.
"Isn't it true that, under draconic law, any creature that kills the Dragon Lord immediately afterward becomes the new Dragon Lord?" Twilight asked sinisterly. "If that is so, then young Dragon Lord, prepare to die."
"Hold it!"
Twilight turned to see who would dare interrupt her on such a historic moment, then widened her eyes in shock when she saw that it was none other than Rainbow Dash, clad in a red baseball cap turned backward with a light blue turtle creature with a propeller cap on its head standing beside her. In her hooves, she awkwardly held a massive book, frantically flipping through it to find out what to do next.
"Twilight, I challenge you to a Pokemon battle!" Rainbow said.
"Curses!" Twilight shouted. "By the laws of the Pokemon world, I cannot refuse your challenge!"
"Then it is a battle we shall have!" Rainbow said.
Suddenly, Discord appeared in the cave, sitting on a rock near a cave wall and eating a bag of popcorn.
"I'll go first!" Twilight proclaimed. "Klefki, use Light Screen!"
Twilight's Klefki began to glow pink, with patterns on its skin that swirled like a lava lamp.
"Now my team's Special Defense is raised by 50%!" Twilight said.
"Capital move, Twilight! Absolutely spiffing!" Discord munched some more on his popcorn.
Rainbow Dash leafed through her book, a drop of sweat forming on her forehead, before finding a move that she liked. "Alright, Tank, use Hyper Beam!"
Tank turned to his master and gave her a very confused look, as he did not, in fact, know Hyper Beam.
"Oh come on, you don't know that move?!" Rainbow kept flipping through her book. "Hey, your Klefki is weak to fire, right? Then I've got the perfect move! Tank, use Flamethrower!"
Tank, Twilight, and Discord facepalmed and shook their heads in response to this.
"What?! What did I do wrong?!" Rainbow asked.
"'Oh, it's a Water type, so it obviously must know a Fire-type move!'" Discord said mockingly.
"Alright, alright, I'll pick something else!" Rainbow flipped through her book once more. "Aha! Here's a cool move! Tank, use Explosion!"
Discord burst out laughing at that, and could barely compose himself. "You know, normally Squirtle doesn't learn Explosion at all, but I suppose I'll make an exception for this time." Discord snapped his fingers.
Tank exploded.
When the dust settled, Twilight and Rainbow were lying on their backs, limbs splayed out at random angles. Rainbow's baseball cap was nowhere to be found. Twilight's Klefki lay defeated and completely unconscious, as did Tank, who was now back to his original form as a more-or-less regular tortoise.
Rainbow sat up, coughing her lungs out. "Does this mean I win?" she said.
"Well, as far as I'm concerned, you both lost," Discord said amicably.
Twilight also sat up, moaning in pain and bracing her head with one hoof. "What happened?" she said.
"You became a bloodthirsty maniac and almost conquered the Dragon Lands because of Discord's shenanigans?" Rainbow answered.
"What?! Discord!" Twilight shouted.
Discord laughed with amusement. "Oh, you didn't think I'd let you commit murder, did you?" he said.
Twilight growled with rage. "Come on, Rainbow Dash, let's get out of here." Twilight and Rainbow soared out of the cave, with Tank in hot pursuit, leaving Discord and Ember alone in the cave.
"What in Tiamat's name did I just witness?" Ember asked.
"You know, I really couldn't tell you," Discord said.
Author's Note
That moment when you finally find a shiny Squirtle and it uses Explosion. 
Also, if you want to see the Mane Six and others fighting off Pokemon to defend their homes, all you have to do is ask. I might get around to it at some point.
