"We need to go through a magic mirror to a world populated by sapient mostly hairless apes. I understand we'll be transformed into a member of the species ourselves once we go through, but--"
"No, I know about that, Sunset's explained all that to me. I'm just... wondering how this happened. What's going on? Why do we need to get over--"
"Look," Starlight said flatly. "You were the one that made her in the first place, right?"
"Um. Yes."
"So if anybody's going to stabilize her morphic outline it's probably going to be you."
Sunburst blinked. "Her morphic outline's destabilized?"
"Pretty dramatically, yeah. It--" Starlight paused. "...Well. The best way to put it is it fragmented, but that doesn't quite convey the scope of the problem in its entirety..."
"Oh my goodness. What's the extent of the damage?"
"...you really won't believe me until you see it for yourself. And to see it for yourself, you need to get over here and jump through a magic mirror and become an ape. Can you do that?"
"Well, I'm in the Crystal Empire right now," Sunburst pointed out. "And you're in Ponyville."
Starlight rolled her eyes. "Obviously I want you to buy a ticket and ride the train. Unless these changeling beetles can serve as portals as well as communication devices."
"Vocoleoptera."
"What?"
"They're called vocoleoptera." Sunburst cleared his throat. "From the order coleoptera, which contains all known beetles and itself a derivation from old pegasus words koleos and ptera, meaning sheathe and wing respectively, combined with the word vocal, which--"
"Sunburst, normally I would love to listen to your lectures on magic and history and all that you know, but your sister is in serious danger and I need you here as soon as possible!"
Sunburst adjusted his glasses. "Quite right, quite right. What should I bring, do you think?"
"All the books you used to make her in the first place," Starlight suggested. "And anything about mental... stuff."
"Mental stuff?"
"Like, uh, how the mind works, how it can be torn apart, that sort of thing."
Sunburst frowned. "Starlight... what exactly happened to Sunset?"
"I... well..." Starlight bit her lip. "So, apparently she's regularly transformed via magic while she was on the other side, and I got a little curious and I asked her about all her transformations and, she kind of thought it might have been due to emotional, uh... the point is we agreed to an experiment--which she designed!--and that we took all sorts of precautions, and now there are like seven very different Sunset Shimmers running about the other world."
"Ah, a fractal morphic cascade. I'd say that was purely theoretical, but it is Sunset we're talking about here."
Starlight blinked. "Wait, that's it, you believe me? Just like that?"
"Well, you wouldn't be using a vocoleoptera if you weren't serious about this. I mean according to Thorax, they're one of their most highly demanded exports, but they're so rare that getting a hold of them is incredibly difficult and learning how to use them is actually surprisingly complex." Sunburst paused. "Granted, you are a genius and you live with a princess, so neither factor is as much of an issue as it would be for the common pony, but the point remains."
"So the only reason you believe me is because I'm using an expensive and hard-to-use method to contact you," Starlight deadpanned.
"...Um." Sunburst coughed. "The way you worded that implies I don't trust you normally, which is certainly.... not the impression I wished to give, because I do. Trust you normally. I trust you. And that means I take what you say seriously. So I believe you, because I trust you, and I trust you not to abuse resources to contact me about a situation I don't need contacting about. This is what I wanted to communicate."
"Well, that's a nice save." Starlight sighed. "I'm sorry, I just... I feel like this is my fault, you know? Even if I never expected this and wasn't the person to design the experiment, the point is I'm just so worried that I've done something which can never be fixed. I tend to get that feeling a lot, now that I think about it."
Sunburst frowned. "...But you've always found a way to fix things, haven't you?"
"Not without help."
"There are very few things a pony can do without help. Being able to recognize one needs help is one of them. And of course I'd be willing to help you. I just have to get on a train and ride to Ponyville which... is going to take a bit of a while, you understand."
"Of course." Starlight nodded. "Look, the situation is weird and complicated and I think it would be best if I was on the other side of the mirror for the moment. I don't know if this form of communication works between universes, so--"
"I'll have Twilight use her journal to contact you when I'm at her palace."
"Makes sense. So... uh... yeah. Come here soon. Bye, I guess."
"Good luck and fair fortune, Starlight Glimmer."
The fiery circle flashed out of existence, leaving the unicorn to stare at the black beetle in front of her. "...Good luck and fair fortune. Two things I've never had." She took a deep breath. "Oh please, whatever sick gods and forces of nature have made me their plaything, don't let this situation get any worse for Sunset..."