Pinkie Pie saw Pinkie Pie bouncing around Ponyville, plotting her next party.
Wait, what?
Yes, Pinkie saw herself bouncing from house to house and handing out party invitations. Except that, obviously, that pony wasn't Pinkie. It couldn't be. Not even Pinkie could be in two places at once--at least, not in this particular context. It wasn't Pinkie. It was a changeling. Well, that, or there was a second frizzy-maned bouncy pink party pony who was friends with everypony in Ponyville.
Yeah, it was a changeling.
Naturally, Pinkie wasn't at all thrilled with the idea of a changeling throwing a party for her friends. In fact, that was something her unofficial job as Party Pony required her to prevent! After all, if a changeling was throwing a party, it was obviously going to pervert the beauty of a party to do something nasty. But what? Maybe...maybe Pinkie had a secret admirer, and the changeling was using the party to find him, hook up with him, and feast on his desires! Pinkie shuddered. (But she had to admit that having a secret admirer would be pretty fun. Just not the whole desire feasting thing.)
Or worse...glue! When you start thinking about glue, Pinkie thought, you know it's time to stop thinking and start partying. In this case, however, "party" meant "make sure the meany-pants pony doesn't hurt any of Pinkie's friends." And that meant stalking this changeling.
===
Not-Pinkie bounced up to Carousel Boutique with a basket-hat full of invitations. These invitations were done up in typical Pinkie Pie style: mass-produced chaos. Each invitation, like every other, was a one-of-a-kind festivity in its own right. If somepony as prim as Rarity tried very hard, she might be able to throw a party almost as fun as one of Pinkie's invitations.
Rarity had tried once. Just not very hard. Her party was slightly more fun, at least, than waiting in line at the Carriage Registration Office while trying not to forget that you have to pick up the dry cleaning at the other shop this time around. At least Pinkie's parties, though they were artistically bankrupt and unsophisticated, were fun. And Rarity, despite appearances, had no objections to a bit of simple fun.
"Good afternoon, Pinkie Pie. That hat...didn't you wear something similar on the day we threw you a surprise birthday party?"
"Yep! It worked really well, so I wanted to try it again. So, wanna come to my 'every Sunday this month is divisible by seven' party?"
Rarity pulled out a pink-and-green invitation. She glared at the garish monstrosity. "Really, Pinkie? I know your designs are, well, unique, but I would say you've overdone it on the bright colors."
Not-Pinkie shrugged. "What can I say? I love bright colors!"
"Yes, Pinkie, but I can't even read this invitation. Most of the letters are the same color as the background, or at least too close for comfort."
"Wait, what? Let me see that invitation." Rarity showed it to not-Pinkie, and sure enough, most of the letters were unreadable. A pony with good vision could make out "YO VIT ," "orner," and "HEN," but nothing else. "Whoopsies. Well, it's at Sugarcube Corner at seven next Sunday. You coming?"
"But of course!"
===
Not-Pinkie bounced to Bon Bon's house, oblivious to the not-bush following her, piloted by none other than the hitherto inimitable Pinkie Pie. The latter was rather impressed by how well Fakie Pie--the name she had given to not-Pinkie--was emulating her. Wait, no! She shouldn't be impressed at the bad guys! She should be getting rid of them! But how could she do that?
Throw a counter-party? No, that would be really confusing, having two parties going on, and some ponies would go to the fake one, some to the real one, and it just wouldn't work.
Party Cannon the Fakie Pie in the face? Nope. She didn't have any party shells left after the royal reception, and she hadn't gotten around to stocking up. Would be a great idea, though.
Just run up and buck Fakie Pie? No. Terrible idea, even by Pinkie standards. Pinkie hadn't (deliberately) bucked a pony since she was a filly. For that, she had to do limestone duty for months. Her hooves still got itchy at night sometimes. Still.
What did Pinkie do the last time someone was causing trouble in Ponyville and she was the only one who knew that there was even a problem?
Pranks.
This prank was deviously simple: show up to the party. That was it. No joy buzzers, water balloons, or hot-sauce cupcakes, although Pinkie would love to force-feed some to this changeling scum. By showing up, Fakie Pie would be revealed, and Pinkie and her five best friends could enact sweet, sweet, sugary revenge on the changeling. It was completely foalproof. No, really. Not even the Cake twins could mess it up.
At this point, Pinkie would have hit up Rainbow Dash and started planning the details of the prank, but there weren't any actual details to plan, so she just waited for Fakie's party.
===
Sugarcube Corner was closed. When Sugarcube Corner closes at 6:00 p.m., odds are reasonably high that it will become a party palace within the hour; the small herd milling around it would confirm any such suspicions. Almost a dozen ponies, including Pinkie Pie's closest friends (plus a few who were invited just because,) were biding time until they were invited in.
"Judging from the number of guests, I expect that this is going to be a relatively simple, low-key affair. Don't you agree, Fluttershy?"
"Oh, yes, Rarity. Pinkie wouldn't bother inviting me if things were going to get loud and crazy. Still, this is an awfully big crowd..."
"Relax, Fluttershy. It's just the six of us plus, oh, it looks like four--five more? Is that Lyra over there? You simply must get to know her, Fluttershy; she is a wonderful musician! I don't think I've ever heard a soloist as talented as her."
"Oh, Lyra? Isn't she friends with Bon Bon? Well, I--I don't really..." Fluttershy's voice trailed off, and she retreated into her mane.
"Fluttershy, is there a problem?"
Fluttershy remained obscured by her mane. "Well, remember that assertiveness seminar I went to? Bon Bon was there, and she--"
The wholly unsubtle sound of a noisemaker tore apart all conversation and announced the entrance of the pink hostess. "Alright, everypony! Come on in!"
===
Even a catsuit-clad Pinkie Pie was glaringly obvious. Despite the sunset giving way to dusk, Pinkie's bouncing pink tail was a dead giveaway. She didn't care very much. Being sneaky wasn't part of the prank. Heck, she didn't even need the catsuit. It was just for fun, as was the plan she had concocted to enhance the simplest prank ever devised.
She mentally rehearsed her plan one last time. First, crash the party at a suitably dramatic time. Not right at the start, that was too boring, but not too late that the changeling got to eat everypony's love, either. Second, draw attention to herself. Like, when she showed up, she would shout "Hello there, Pinkie Pie," because that would make it obvious that there was an impostor, and the tension it would create would force somepony to do something. Fourth, party!
This was the best plan, Pinkie thought, that she had come up with since throwing the prank-party for Gilda. After storing the catsuit in a tree (rather than disposing of it, because what if there was a catsuit emergency?), she took a deep breath. It was time.
===
Everypony was having a wondrous time at the party. The punch was delicious (and Gummy-free!), the music was exceptionally danceable, and, best of all, Pinkie Pie just showed up. It was sure to be a great party, since Pinkie had the great sense to invite--
Wait, what?
There was Pinkie, flailing like a madmare on the dancefloor. But...there was Pinkie, milling about in front of the door.
What.
===
"Oh! Hello there, Pinkie Pie."
Pinkie shot a venomous smirk at Fakie Pie. The jig is up. Jigs don't even go well with this music. The real Pinkie would have picked more appropriate music.
Fakie Pie gasped. It was a really good impression of the famous Cake family gasp that Pinkie had picked up. "What? Yeah, I'm Pinkie Pie, but...so are you! No, that can't be it! I can't be in two places at once now!"
Pinkie glared. "You--you're a changeling disguised as me so that you can find ponies to feed off of!"
"What!? That's ridiculous. Only a changeling could come up with something that silly! Well, I could too because I can get pretty silly, but at least I wouldn't accuse ponies of being changelings without proof!"
"Proof? PROOF? Who needs proof? There are too many Pinkies! That's all the proof I need to know you're a changeling!"
"No, there's one Pinkie, and there's some sort of mean--"
Twilight Sparkle teleported in the middle of the two, cutting the argument short. "All right, that's enough. I'm just going to dispel the changeling's disguise and get this over with." Twilight furrowed her brow, glancing between the two Pinkies.
Abruptly, she hit Pinkie Pie with a burst of magic. Pinkie felt momentarily different. However, she wasn't any different at all after that; she was still Pinkie Pie.
Twilight was nonplussed. "Well, uh, hi there, Pinkie. Guess the one who threw the party was the changeling. That was unexpected, but there's twelve of us and one of it."
Another burst of magic. Fakie Pie flickered violet, but was otherwise unaffected.
For a moment, nopony spoke. Then everypony spoke, and they all said the same thing:
"Huh?"
===
"But...that's not possible!" Twilight said. "If there are two Pinkie Pies, and neither is a changeling, then...what happened?
Applejack walked up to Twilight. "Twi, I'm sure Pinkie's just pullin' a prank. Shoot, I bet any minute now, Ditzy Doo's gonna come out of a Pinkie costume or somethin'."
"No I'm not!" Ditzy said. "That's just silly, Applejack." Ditzy then threw a ball of used muffin wrappers at Applejack.
Rarity stepped forward. "In this case, it seems we will have to take drastic measures. And I know just the thing!"
"Drastic measures? What the hay are ya gonna do, Rarity?" Applejack looked at Rarity.
"I'll throw both Pinkie Pies a party!"
The Pinkie who threw the party looked horrified. "N-n-no thank you, Rarity. I'm flattered, but I think I'll pass."
The other Pinkie, though, the one who crashed the party, she was excited. "Yes yes yes thank you so much Rarity I'm so excited!"
"That's the real one," Rarity drawled, pointing to hostess-Pinkie.
"But Rarity, how can you tell from that reaction?" Twilight asked.
"Darling, have you been to one of my parties? They're terrible! Especially for one as, ah, unrefined as Pinkie Pie. I invited her to a small gathering, and she was bored to tears. Obviously, she wouldn't exactly be thrilled to attend another one, so the one who reacted with horror--don't worry, Twilight, I am far from offended--the horrified one reacted appropriately, while the one who reacted joyously is little more than a shallow imitation of Pinkie."
"I guess that makes sense," Twilight said. "But then...who's the other Pinkie?"
"Um, girls--" Fluttershy tried to interject and failed miserably, for The Other Pinkie had begun a tirade.
"I'm Pinkie Pie, of course, but you mean ponies evidently won't believe me just because I had the bad luck to be excited about a party!" The Other Pinkie stared Rarity down, eyes filled with indignant rancor. "I mean, 'shallow imitation?' What kind of reaction is that?"
"Girls, could you--"
"I was hoping that you, Rarity, would at least show me a little generosity. But no, it was a trap!"
"--isn't quite as--"
"A TRAP! You took the most beautiful thing in the world and turned it into a trap, just so you could trip up poor widdle Pinkie, instead of dealing with the changeling running freely in Ponyville! Do you ponies even care about Ponyville?"
"--girls, please listen--"
The Other Pinkie turned to hostess-Pinkie. "And you." Hostess-Pinkie reflexively took a step backwards, as The Other Pinkie took a step forward, moving in for the kill, eyes aflame with hatred for the defenseless pink pony.
"Horse off, clop-face."
===
Hostess-Pinkie froze.
Then she started tittering. "'Clop-face'? That, that's just--that's the silliest insult I've ever heard in my entire life!" Hostess-Pinkie proceeded to giggling. "I mean, what does that even mean? Are you trying to say I walk with my face?" And hostess-Pinkie had devolved to rolling-on-the-floor laughter. "Hahaha, 'horse off,' hahaha..."
Everypony else was laughing, too, except for The Other Pinkie. "What's so funny? This isn't funny! This was never supposed to be funny! You should be cowering in shame, not laughing!"
But everypony ignored her. The laughter eventually died down naturally (except hostess-Pinkie, who continued rolling around,) leaving Fluttershy free to speak. "Well, now that we're all quiet, I'd like to point out something."
"Yeah, Fluttershy?" Rainbow Dash asked.
"The angry Pinkie is a little bit gray."
"That explains everything, Fluttershy!" Something had clicked in Twilight's head; this saturation difference was apparently the last piece of evidence needed to solve this mystery. "The other Pinkie is a Delusion! Delusions are rancorous spirits that take the form of a pony and spread lies and disharmony among that pony's friends. In fact, their imitation is so superficially accurate, they actually think they are that pony."
"So they're like Discord mixed with a changelin'?" Applejack asked.
"You could say that. In fact, Discord used an army of them in an attempt to destroy ponykind, back before the Princesses defeated him the first time. Most of the Delusions are sealed in Tartarus, so I don't know how this one got free. We'd better get the Elements of Harmony."
"But we can't just leave this thing free to run around Ponyville," Rainbow Dash said. "There's no telling what it might do."
"Don't worry, girls, I have a plan."
===
"Let me go, you namby-pamby losers!" Delusion-Pinkie, spouting TV-Y vulgarities, was stuck in a field outside of Ponyville. Thanks to the cabal of background ponies tasked to guard it, the Delusion was hog-tied and strapped down, with one end of the strap pegged in, and the other held down by Bon Bon's hoof.
"I still hate my parents for naming me that," Namby-Pamby said, using her magic to rip off a stud from her foreleg-collar. "This a good enough nail, Bon Bon?"
Bon Bon looked at the stud, which was long enough to be called a spike. Who would expect, Bon Bon thought, that the adolescent filly's ludicrous fashion sense would ever in handy? "That should work, Nam. You'd better get home soon, by the way, because I know breaking curfew is something your parents won't put up with."
"You mean 'up with which my parents won't put.' No wait...er, forget it. Thanks for letting me tag along, you two."
"No problem, Nam," Bon Bon said. "We'll be seeing you."
"Glad you came, Nam!" Lyra added, and Nam left. "Now," Lyra said, turning to Delusion-Pinkie, "we add the finishing touch to this." Lyra held the spike in place, and Bon Bon stomped it into the ground.
"All of you! All of you are changelings!" If Delusion-Pinkie were a pony, one would call her stark raving mad, but this was apparently par for a cornered Delusion. "The Princess will kick your sorry butts into dragon territory, you villainous scum!"
"There!" Bon Bon said, doing her best to ignore the captive. "That should keep it until the Elements arrive. Now, it's getting late, but one of us has to stay to guard it."
Ditzy Doo jumped up and down. "Pick me! Pick me!"
Bon Bon cocked an eyebrow and looked Ditzy straight in an eye. "Ditzy, never in a thousand years would I leave you alone to guard a dangerous creature straight from the bowels of hell."
"But it's tied down really well, and I promise not to mess with the strap or the ropes or anything!"
"Ditzy--" Bon Bon began, but Lyra interrupted. "We appreciate the offer, Ditzy. (yes we do, Bon Bon, can't you just be charitable for one moment?) But it might take a while, and you don't want to leave Dinky all alone for so long, right? And don't you have to get up for work super early?"
Ditzy smiled. "Nah, Dinky's spending the week at Sparkler's, and I have tomorrow off. I'm telling you, I can do it. Besides, I want you two to get some sleep yourselves."
"When you put it that way," Bon Bon said, then yawned, "I'm far less opposed to the idea now. Come on, Lyra, let's hit the hay."
"All right, Bon Bon, but I'm going to bed right after." Lyra and Bon Bon left, leaving Ditzy alone with the Delusion. Ditzy produced a box of muffins and began eating one, keeping an eye on Delusion-Pinkie--and another on the muffin she was eating, so she wouldn't make too much of a mess. Being wall-eyed did have its advantages.
"Oh, great. They're mocking me. They're seriously mocking me. They left just one changeling to guard me, and they made it look all derpy. Those guys are seriou--"
Half a dozen muffins found themselves stuck in Delusion-Pinkie's throat. Ditzy, meanwhile, stood over the Delusion, giving it a glare. Ditzy's eyes oscillated, which made her glare somehow more menacing. Those who knew Sparkler or Dinky well had heard of Ditzy's legendary glare, second only to Fluttershy's Stare itself. It was enough to give a Delusion pause--and the muffins certainly didn't help.
Ditzy went back to her post and unwrapped a second muffin. Ponyville has never had a Delusion problem since.