Days passed. Sunset, Twilight, Kim, and Ron researched everything they could in the Athenaeum, then returned to Ponyville. They gathered their friends together for a war council.
"So here's the plan," Twilight said. "I'm going back through the portal with Sunset, Sonata, Kim, and Ron. With our research and the other Twilight's help, we're hoping we'll be able to disentangle this mess of mixed magics. After that, the other Twilight will take Kim and Ron on their quest to save their home." She glanced at Sonata. "I know you want to stay here in Equestria, but right now, we need to figure out the extent to which your magic is going to regenerate." She paused, then added, "And frankly, if you can be trusted. I think you can and so do my friends, but we've been burned by 'reformed' dark magic creatures before. I'd feel a lot more comfortable about letting you come back to stay if you prove yourself first."
Sonata's maw crinkled. "Like...maybe helping Kim and Ron save their world?"
"That's what I was thinking," Twilight said, nodding. "I know how capable Kim and Ron are—or at least, how capable they tell me they are—but I don't know what the other Twilight is capable of, and honestly? I'd feel better if they had somebody else going with them."
"Hey, the more the merrier," Ron said.
"I'll help too," Sunset said.
"No," Twilight said, shaking her head. "I need you to do something else for me."
Sunset blinked. "Something else? What?"
Twilight levitated a five-pointed amethyst crown out of her saddlebag and placed it atop Sunset's head. "I need you to fill in for me here," she said.
Everyone stared at her.
"Wait...what?" Rainbow cried.
"You're not going with them on this absurd quest, are you?" Rarity asked, blinking rapidly.
"No, I'm not," Twilight said. She took a deep breath. "I'm taking the other Twilight's place at Crystal Prep until she gets back. We may have dragged her into the middle of our little misadventure, but that doesn't mean we can just uproot her life."
The others stared at her.
"Uhh...are you loco in the coco?" Pinkie asked. "I mean, I know if I traded places with the other Pinkie Pie I could probably pull it off because I'm Pinkie Pie, but do you think you'll be able to be a whole other Twilight Sparkle without, y'know...getting caught?"
"Ah agree," Applejack said. "This has bad idea written all over it."
Twilight shrugged. "From what Twilight tells me, she pretty much keeps to herself and does her own research. She doesn't have any friends and her teachers don't really bother her. If she leaves enough notes on what I need to know, I can fake it long enough."
"And Princess Celestia is okay with this?" Sunset asked.
"More or less," Twilight said. "Besides, if any real emergencies come up back here that need my attention, I can always hop a bus back to CHS and come home." She smiled reassuringly. "Just trust me, okay? Besides, you'll do fine as interim Princess of Friendship."
"Uhh...yeah, about that," Sunset said. "I, uhh..."
"Just follow my schedule and Spike will tell you whatever you need to know," Twilight said reassuringly. "It's not like I even really do all that much right now, so just...think of it like a little vacation back home!"
Sunset stared at her for a long moment, then sighed. "Okay, I'll do it," she said. "We'll need to explain it to my friends and Principal Celestia though."
"Of course," Twilight said.
"We'll be here for you, Sunset Shimmer," Fluttershy said reassuringly.
"Yeah!" Rainbow said. "I mean, it's way past time we all got to know you, right?"
Sunset smiled. "Thanks, everypony."
* * * * *
Twilight, Sunset, Sonata, Kim, and Ron got off the bus at the gates of Crystal Prep. "Wow, this place looks...boring," Sonata said.
"Yep, this is a prep school," Ron said.
Twilight adjusted the wig and sunglasses Rarity had given her. "Let's go," she said.
The group walked up to the doors and entered the cold, austere halls. "So...which way do we go?" Sunset asked.
Twilight paused. "That's...a good question." She looked around. "I think—"
"Twilight? What the heck are you wearing? What's up with the wig? And who are these people?"
The group stopped short as a pink-skinned woman with long, elegant three-colored hair walked up to them, the heels of her gold pumps clicking on the marble floor.
"Oh! Um, hello," Twilight said, waving sheepishly. "I...wasn't expecting to run into you out here! These are, umm..." She looked at her friends.
"A delegation from CHS," Sunset lied smoothly. "We're looking to remodel a couple of our science labs, and we heard one of your students had a state-of-the art lab here, so we wanted to take a look and get some ideas."
"Oh! Well...I hadn't heard anything about that, but—"
"There you all are!" Twilight yelled breathlessly as she skidded around a corner, charging up to them with her glasses askew and her hair out of its bun. "I should've gotten a cell number for...but then I remembered I don't even have a phone, and I..." She trailed off. "Oh, umm...hi Dean Cadance. I—"
Dean Cadance held up a hand to stall her as she looked, wide-eyed, between the two Twilights. "Twilight?" she asked the newly-arrived Twilight. "Why are there two of you?"
"Two of me? Heheheh, what do you..."
Princess Twilight sighed and removed her wig and sunglasses, shaking out her long violet hair. "Don't bother," she said. "Cadance? Sorry about this, but we really can explain..."
Twenty minutes later, in Dean Cadance's office...
"So...none of you are from this world?" Dean Cadance stared around at the group of teenagers. "And you need Twilight's—I mean this Twilight's help to get home?"
"These two do," Princess Twilight said, indicating Kim and Ron. "The rest of us can just go through the portal to Equestria that's at Canterlot High School. Except Sunset Shimmer actually lives here in your world and goes to CHS." She paused. "And, well...I'm going to be taking this Twilight's place here while she helps Kim and Ron get home."
"Uh...huh," Cadance said slowly, pursing her lips.
Twilight sighed. "Look...Dean Cadance...just pretend you never saw any of this, okay? Please? In a couple of hours, these three won't be here anymore, Sunset Shimmer will be back on the bus to CHS, and there'll only be one Twilight Sparkle at Crystal Prep, just like always. It doesn't matter that she isn't me, she can be me. Just...help her be a little more me than she is now maybe?"
Cadance pinched the bridge of her nose. "I'm dreaming this," she muttered. "I'm dreaming this, and none of this is real..." She looked up, forcing a bright, happy smile onto her face. "Right! Okay! I'm going to sit right here at my desk for about...three hours? At which time I'll drop by the lab to check on you, Twilight. And you'll be the only one there, because the rest of you don't exist, right? And you won't say anything...crazy, right?"
The two Twilights looked at each other.
"Cross my heart, hope to fly, stick a cupcake in my eye," Princess Twilight said, going through the gestures of a Pinkie Promise.
"See, that right there is what I mean by 'anything crazy'," Dean Cadance said flatly. "Just...just get into a Crystal Prep uniform or disappear or whatever you're going to do, but..." She sighed. "I'm sorry. I just..."
"We'll get out of your hair now," Sunset said.
"Your very pretty hair," Ron put in.
"I'm SO jealous of your hair," Kim added.
Cadance glared at all of them. "Thank you," she said tersely.
"Right!" Twilight said, clapping her hands together. "Let's get to the lab and make science happen. Enjoy the rest of your definitely-not-going-crazy dream, Dean Cadance!"
The group hastily left the office. "Well...that went well," Princess Twilight said.
"I like her!" Sonata said, giggling. "She's funny!"
As the group proceeded to the lab, they failed to notice a blue-skinned girl with frost-colored hair done up in massive twin pigtails and salmon-framed glasses watching them, a frown on her face. "Twilight Sparkle's up to something," she said to nobody in particular. "I should keep an eye on this."