((Prompt: Lies and misdirection.))
((Note: The [No Tag] is there to keep from spoiling the end.))
It was nearing sundown when Twilight Sparkle knocked on the door to Fluttershy's cottage. Inside, she could hear a short string of hushed curses followed by two sets of hooves scuffling across the floorboards. There was a loud thump, and Twilight could hear her friend yelp.
Finally, after a minute of this, Fluttershy opened the door, though only just wide enough to poke her head through. “Oh, hello Twilight! I, um, didn't expect you here right at this moment.”
Twilight raised her head, trying to see past Fluttershy into the cottage. “Is everything alright, Fluttershy?”
Fluttershy raised her head as well, blocking her view, and laughed nervously. “Everything's fine, Twilight! It's never been better!”
“Who were you just talking to?” Twilight asked.
“Myself,” Fluttershy said, nodding her head. “I was talking to myself. 'Oh, Fluttershy,' I was saying, 'the sun's about to set and you still don't know what you're going to have for dinner!' I'm uh, very indecisive like that.”
Twilight frowned briefly. “So there's nopony else here?”
Fluttershy shook her head. “No, definitely not. Just me and all my animals, that's all.”
“You haven't seen Rarity?”
A bead of sweat formed on the pegasus's brow. “Um, not since our spa date, no. Why?”
Twilight shrugged. “I thought I saw her headed this way. Strange.”
“Well, I don't know what to tell you, Twilight. There's no Rarities here.” Fluttershy gave Twilight a weak grin.
Hooves thumped against the floorboards upstairs. Both Twilight's and Fluttershy's eyes shot up to the ceiling.
“What was that?” asked Twilight.
“Nothing,” Fluttershy quickly replied. “Just... Carrie, the capybara, getting into my horseshoes. I should probably go check on her.” She began pulling the door shut.
“I could help,” Twilight offered, pushing on the door.
“No!” Fluttershy held the door firmly with her hooves. “She's uh, very shy.”
Twilight studied her friend's expression carefully. After a moment, she gave Fluttershy an understanding smile. “Okay, Fluttershy. If you see Rarity, please tell her I'd like to talk with her.”
“I will tell her the next time I see her,” promised Fluttershy. “Whenever that is.” She pulled the door shut.
*
The yellow pegasus kept an ear to the door, listening to the sound of Twilight's hoofsteps fading away. A smirk spread across her lips.
The smirk remained intact even as magical green flames flickered and changed them from yellow to white. Changeling magic flashed, and where there had been Fluttershy, there was now Rarity, grinning triumphantly as she sauntered up the stairs.
“That was too close,” she said as she pulled open the bedroom door. Inside, bound by thick, sticky green goo, the real Fluttershy struggled and murmured into her gag.
“Mmmh! Mrrh-m-mh!”
The changeling flicked her head, setting a lock of purple hair askew on her face. “I do wish we had the time for a chat, darling, but your nosy friends have me on a bit of a timetable, so I'm afraid we have to get right down to business. Now, let's see if we can find that pesky memory where you found me out...” Her horn glowed sickly green. Fluttershy's eyes widened in fear.
Zzap! The glow in Rarity's horn vanished, and her eyes lost focus. She listed to the side and then slumped to the floor. Green flames crackled as the changeling reverted to its original insectoid form.
Twilight stood in the doorway of the bedroom, panting. A wisp of steam rose from her horn. “That's for thinking I bought your Fluttershy act for a second!”
A few moments and a flash of magic freed Fluttershy from the changeling goo. “Twilight!” she cried as soon as her mouth was free. She threw her forelegs around the alicorn. “How did you know it wasn't me?”
“Your capybara is named Candy, not Carrie,” Twilight explained. “That's something you would never get wrong.”
Fluttershy glanced down at the unconscious creature on her floor, and shivered. “Wh-where's the real Rarity?”
“I don't know.” Twilight nudged the thing with her hoof. “But we're going to find out.”