"Okay, girls, I'm sure you're all wondering why I called you all here..."
"What is it, Twi?" AppleJack asked
"Yeah, what's happening?" Rarity looked to Rainbow for some clue, only to find that the pegasus was distraught, and didn't seem to want to look her in the eyes.
Twilight answered, after a moment of thought. "Something's about to happen. Something big. It could change everything... and it might even mean the end of the world as we know it."
"Oh dear," Fluttershy muttered as she lowered her head to the floor.
AJ rose up to the occasion, not willing to go without a fight. "Can't we do something about it?! What about the Elements of Harmony?"
"I'm afraid this is beyond the Elements."
Everypony's eyes widened in shock.
"W-what is it?" Fluttershy asked.
"I don't completely understand it. It's... Pinkie? Can you explain it?"
"Okay, so it's like..." she pouted as she thought. "So imagine if you were living on a balloon, right? And you thought that the balloon was EVERYTHING!"
"Everything's a balloon?" AJ asked.
"No, the balloon is everything."
"That's what Ah said."
"No, other way. So a balloon is everything, but then it turns out that our balloon is just a tiny piece of a bigger balloon that is actually everything."
"So... Everything's a bigger balloon?"
"No, the bigger balloon is everything!" Pinkie retorted, slightly frustrated by AJ's lack of comprehension. "Since our balloon is inside the other balloon, things can move back and forth by way of the—" She allowed her voice to waver spookily as she continued, "third dimension!"
"Uh... What?" AJ moved her hoof all around. "That s'posed to be special or somethin'? I'm lookin' at three dimensions right here."
"Oh, I forgot, also you're living on the balloon and you can only move around on the surface, not up and down and all around like normal."
Rainbow tilted her head. "What?"
"So the third dimension is actually a fourth one!"
Rarity broke in. "Wait, I'm confused, can we start over?"
"Okay, I'll try explaining a different way. So imagine the universe is a big chocolate cake layer, but then it turned out that the cake was just part of a big cake-cake."
"A giant cake with cakes inside of it."
"Why would you ever—"
"Ummm, because it's delicious? Why wouldn't you—"
"Pinkie," Twilight interrupted, "the spatial analogy isn't important, just explain the consequences."
"Right. So, sometimes, things happen out there in the big balloon that affect us down here in the little balloon!"
"Well..." Pinkie gritted her teeth.
Twilight broke the news so Pinkie wouldn't have to. "We might only have an hour left to exist."
"What?" The others asked in unison, as they gave each other uncertain glances.
"What do you mean, Twilight?"
"Pinkie is slightly displaced in the fourth dimension, which allows me to make unusual kinds of measurements with her help. I can get some insight into the outerworld, and I can also learn about different spaces and times in our own universe." She glanced down at the floor. "And... Well, I think this is partially my fault."
Everyone just stared at Twilight, waiting for her to go on.
"You see, when we finished Starswirl's spell, it... We... I, forced a billion-trillion quantum mechanical wavefunctions to all collapse in a specific way at that moment. It shouldn't have been possible."
AJ raised an eyebrow. "Quaternary mecha whatsits?"
"They're mathematical functions describing probabilities on a microscopic scale. Normally, they're random, but I violated several laws of physics to make them go a certain way, and now... the universe is re-asserting itself."
Pinkie leaned in offering to carry on the explanation, and Twilight nodded. "When Twilight got all wingy, she accidentally forced the universe to go one way, when it wanted to go a different way. It connected a bunch of parts of our universe together that should never, ever, touch, and it's like somepony's squeezing the balloon."
She pressed a balloon tight between her hooves to demonstrate. "Just like a balloon, it's pushing back out, trying to make itself all pretty and round again," she explained, as she took the pressure off.
"Well can't we force it? Ah reckon we could hog-tie it however we wanted, right?"
"Well..." Twilight began, trailing off as she tried to think of a gentle way to put it.
Every eye darted to Pinkie as the balloon she was holding popped under the force she was putting on it. "Bad idea."
"So that's it, then?" Rainbow asked. "It's all over?"
"Maybe, maybe not," Twilight began, "There's a lot about the universe I don't know. One interpretation, called the multiverse hypothesis, implies that reality will just fragment in a situation like this. When we make the universe go one way, and the outworlders try to make it go another way, it just splits in two, and we can go on our merry way as if nothing ever happened."
Twilight looked down at her hooves, unable to face the hopeful expressions of her friends. "But there's no substantiation for that hypothesis. If any pony had ever been able to see evidence of the multiverse, it would have been Pinkie, and she's never encountered anything like it."
"But..." Pinkie began, as she smiled, "even if it's over for us, the versions of us from before Twilight got wings will still exist!"
"But... What about Twilight?" Rainbow asked.
"She'll be okay, too!" Pinkie announced.
"No... She won't." Rainbow insisted, as she hovered over to Twilight and laid a hoof across her whithers. "Twi, you told me about how that spell worked. You told me about the quantum thingies. If you hadn't forced that stuff to go the way it had, you would have died during that spell."
Twilight turned her head away so that Rainbow couldn't see her eyes. "There's still a chance I could be okay..."
"That's not good enough! I need you to be okay!" Rainbow shouted, choking back tears as she threw her hooves around Twilight's neck.
"Twi will survive," Pinkie insisted, "You guys should seriously start listening to me, I don't say these things if I don't know." She glanced to the side. "The outworlders want her to live."
"Why?" Twilight turned to face Pinkie, revealing that she'd been crying a bit, despite her best efforts to approach the situation objectively. "Why do they care about me?"
"They won't tell me. I don't think they know. They just know that you'll be with us, and you'll still be a princess."
"So... This is all my fault then. The last two years are just going to vanish out from underneath us because of what I did, and I didn't even have to do it?!"
"It's not your fault, Twi, you didn't know—"
"And it's not just me! It's everypony, it's... It's Cheerilee, and Princess Celestia, and Derpy, and Lyra; everyone! Entire Kingdoms!"
"It's okay, Twi, they'll all be there. They'll all be okay."
"I killed two years worth of the whole world! Two years of Princess Celestia!"
"We don't even know if we'll stop existing yet. And even if we will, it was an accident!"
"I already forgive you, Twilight," Rarity offered.
"Me too, Twi. And Rarity... Ah reckon Ah forgive you, too. Fer everythin'."
"You already told me so..." Rarity replied, as she hugged AppleJack, "and that's more than I ever deserved."
"Ah just wanted to make sure you know, jus'incase Ah never get another chance tah say it."
"I don't blame you, Twilight," Fluttershy added. "Everypony makes mistakes..."
"Besides," Pinkie started, "it's possible that this won't change anything. It might just be a huge flush that leaves everything pretty much like it already is!"
"The odds of that happening—"
"Are the same as the odds of you surviving Starswirl's spell..."
Twilight sighed. "I guess you're right..."
Pinkie put her hoof on Twilight's shoulder. "As long as we're all together, that's what matters..."
"How much time do we have left?"
"About forty-nine minutes, now."
Twilight leaned against Pinkie. "I'm so sorry..."
"It's okay, Twi."
"So are we going to watch it?"
"Did you decide you wanted to?"
"I feel like I should know... If I have to stop existing, I want to know why. Unless the girls don't want to... I'd rather be with them than know."
Pinkie nodded knowingly. "Okay, guys... We have a weird opportunity right now. There will be a window opening soon, and we'll have a chance to see the other reality opening while ours might be closing. We'll be able to see what the other-us's are doing."
"I want to see it." Fluttershy announced proudly as she stood up. "I want to be sure that the other Fluttershy will be able to take care of my animals."
"Me too." Rarity insisted. "It doesn't seem like there's anything else that matters quite as much as this."
"Same." AppleJack nodded. "Ah could go back and tell the family goodbye, and scare the bejeezus outa them, but that wouldn't do any good. Ah tell 'em Ah love 'em every day. If there's really nothin' that can be done about this, let's just face it like mares."
"You know my opinion, already" Rainbow stated bluntly, giving a single curt nod.
Pinkie glanced from pony to pony. "Alrighty then, Twi?"
"Let's do it."
All six ponies descended into the basement, where a small theater had been set up. A chair next to the projector had been fitted with straps and scientific equipment that connected the projector to the pony sitting on it.
Pinkie clambered up into the chair, and Twilight strapped her in while the others watched curiously. Twilight expertly manipulated the controls on the projector until a warm pink light was emitted from the aperture.
"Give it a try, Pinkie."
Pinkie concentrated briefly, and a ball materialized on the screen and began bouncing up and down. Then a simplified, animated, version of Pinkie bounced onto the screen and batted the ball off-frame, before running after it.
Twi stifled a bit of laughter as she appreciated her work. "I can't believe this thing actually works... And it might not even exist anymore in forty-five minutes..."
"It's about to start, Twi..."
Twilight nodded as she gestured for the other ponies to come around to the front of the couch so they could sit more comfortably. All of them followed but Fluttershy, who stayed by Pinkie's side.
"Go up there," Pinkie insisted. "Get comfortable."
"I'd rather be here next to you," Fluttershy replied as she rested her hoof across Pinkie's, which was clamped tightly against the arm of the chair.
Pinkie smiled sweetly at her. "I love you..."
"You love everypony." Fluttershy replied as she leaned her head against Pinkie's shoulder.
Pinkie laughed silently as she rested her head on Fluttershy's. "So do you."
They sat together, embracing for what seemed like an eternity.
"Thirty seconds to the event flux," Twilight announced, looking back over the couch at Pinkie.
"I'm ready," she replied with a tearful sniff.
Twilight settled down on the couch and held Rainbow's hoof. Words seemed to escape them both at that moment, but they squeezed each-other's hooves simultaneously as the moment drew nearer.
To their side, AJ was spooning Rarity, who was playing idly with her ponytail.
Pinkie gasped, and the projection phased into static before slowly resolving into the likeness of a few familiar ponies...