Twilight sighed as she flopped onto her bed in her old suite in Canterlot. Shining Armor, her brother, and Cadence, her new sister-in-law, were off on their honeymoon. The excitement of the wedding had burned Twilight and her friends out, and as a result, they were spending the night in Canterlot. Princess Celestia had led her friends to the guest suites, but told Twilight her old suite was still clean and usable, a fact for which the unicorn was grateful. It was nice to spend the night somewhere even slightly familiar.

She fell asleep the moment she hit the covers, and was thus unaware of what would transpire that night.

-----

As Twilight slept, a figure carefully opened the window to her suite. Slipping in, the figure closed it just as carefully. Stepping over to Twilight's bed, the figure smirked, fangs gleaming in the moonlight.

"Twilight Sparkle," the figure hissed, the moonlight showing her for who she was. Queen Chrysalis spoke in a low tone so as to not wake the unicorn. "You were my undoing. I should have made certain to deal with you in a more permanent manner than simply banishing you beneath Canterlot. But I'll make certain that your life is little better than a day in Tartarus after this."

With that, the Changeling queen withdrew a glowing green powder from nowhere, and sprinkled it over the unicorn. "By the week's end, everypony you know and love will turn on you. Despite all you've done for them, they will betray you. This will make certain of that."

Chuckling slightly, Chrysalis departed, sneaking back to her home far across the Equestrian border.

The next morning:

Twilight groaned as the sun shone in through the window. She could have sworn that she had closed the curtains the night before.

She stretched her wings as she got up and jumped out of bed.

Wait... wings?

Twilight turned her head to see two blue wings on her back, small and insect-like. "What is going on here?" She asked herself, trying to stay calm. "Mirror. I need a mirror!"

She rushed into the bathroom and looked into the mirror.

And screamed.

"No!" Twilight wailed. "I'm a monster!"

Indeed, the Unicorn looked very differently. Her coat was black and her mane was blue, though a darker blue than queen Chrysalis's mane had been. There were holes in her legs and in her tail and mane.

But the worst part was her horn, which was now crooked and longer than before.

The finishing touch was the addition of a second horn, shaped like a small crown.

"This can't be happening!" Twilight screamed.

'Knock-knock'

"Twilight?" A voice called out. "Are you okay? We heard screaming!"

Twilight's heart stopped for a second as she recognized Rarity's voice.

Thinking quickly, Twilight threw herself under the covers just as Rarity opened the door. Please, please, please let her not have seen me...

"Twilight? Darling, are you alright?" Twilight heard Rarity trot in, along with the others. "We all heard screaming coming from this room."

Twilight wracked her brain for a solution, and said the first thing that came to mind. "It's... it's nothing, girls. Just a bad dream, nothing more."

"Ya sure, Twilight?" asked Applejack. "You sounded pretty spooked."

Thankful that the bearer of Honesty couldn't see her face, Twilight replied, "Yes, I'm sure. I think I'll stay in bed a little longer, though. I'm kinda bushed from what's been happening the last couple of days."

"No kidding," Rainbow Dash said, stifling a yawn. "I'm still kinda exhausted from pulling a Sonic Rainboom while flying up. Do you know how much work that takes?"

"Well, um, if Twilight wants to stay in bed a little longer, we should probably leave her alone for a while," suggested Fluttershy. "I mean, if the rest of you want to, that is."

"Okey-dokie-loki!" came the cheerful voice of Pinkie Pie. "Just be sure to come down for breakfast before it's all gone, silly filly!"

"I will, Pinkie," Twilight said, though she had no intention of going to breakfast until she'd figured out what the hay had happened to her.

Before anything else could be said, however, Twilight's new body betrayed her. It was a simple, unintentional buzz of her Changeling wings. But in the silence that followed, it seemed to echo menacingly.

"Twilight..." Applejack said slowly. "What was that?"

"Um... some sort of insect?" Twilight suggested. She knew it was hopeless, however. She had felt the covers move when her treacherous wings buzzed.

There was the sound of powerful wing beats, and suddenly Twilight's covers were pulled off. A quick glance revealed that Rainbow Dash had flown off with them, and was now glaring down at the transformed unicorn. "Yeah, an insect called a Changeling!" the pegasus snarled.

Glancing around, Twilight could see that her friends were all glaring at her. Even Pinkie looked somewhat upset. Nevertheless, Twilight gathered her courage and attempted to salvage the situation. "Girls, please listen to me. It's me, Twilight!"

"A likely story!" Rarity said with a sniff. "Why should we listen to anything a Changeling says?"

Thinking quickly, Twilight came up with a plan. "Ask me something only Twilight would know."

"Easy enough," said Applejack with a glare. "How many apple trees did you pick clean by yourself during that one Applebuck season?"

"About... 25, I think?" Twilight couldn't remember all that well, since it had been a while.

Applejack's expression softened for a moment, before Fluttershy interrupted. "That's not good enough, Applejack. We need something more definitive." She stepped up to Twilight. "Um, if you are Twilight, then what was the first animal you tried to help me wake up during Winter Wrap-Up?"

"Snakes," Twilight said simply, shuddering a little. "Followed by bats, bees, and skunks."

Rarity shook her head. "Fluttershy, dear, anypony who wasn't deaf would have heard that commotion. We need something even more specific."

"I've got one," came a young boy's voice. Everypony blinked, turning to behold Spike in the doorway. "What, exactly, did you say to me before I ran off, during that whole thing with Owloysius?"

Twilight winced as her words on that night came back to her, and she repeated them verbatim: "'This is not the Spike I know and love.'"

Spike nodded. "It's Twilight, all right."

Applejack shook her head. "But... but this makes no sense! Twilight's a unicorn, not a changeling!"

"Indeed she isn't," came a serene voice from the doorway. Spike scrambled out of the way, making room for Princess Celestia. Her eyes were stern, and her expression grim.

Twilight gulped. "Princess... please, you believe me, don't you? I'm your student! The one you instructed to make friends at the Summer Sun Celebration? The - "

"That's enough." Twilight snapped her mouth shut. Did Celestia believe her?