Twilight Sparkle stared at her friend as her mind tried to make sense of what her ears had just heard Fluttershy say. There was always the possibility that she had managed to somehow mishear the words. If so, a repetition could make the sentence more comprehensible, so Twilight asked, “Excuse me, Fluttershy. Could you repeat that?”

The book that Fluttershy was trying to shelve fell to the dusty floor, almost followed by the timid pegasus as she sat down hard on the carpet. The air in the dusty library was stifling warm for the afternoon, and the rest of Twilight Sparkle’s friends had scattered to various places in the old rooms of the Castle of the Royal Pony Sisters. In theory, they were dusting, cleaning, and putting the place in order after the harrowing Royal Wedding. In practice, Twilight could hear a few faint snoring noises filtering down from the second floor of the library, indicating several tired friends were taking a brief break. Even Spike was sprawled out over a few books that Twilight was planning on taking back to the Golden Oak library this evening when they all would return to Ponyville.

Fluttershy pawed the dusty carpet once, looking out the nearby open window with an expression of intense longing. “I’m a changeling, Twilight. I think. I mean, when we were fighting those other changelings, I started thinking. What if I couldn’t fight them because I’m actually one of them?”

That was worthy of a Thoughtful Puzzled Expression, 107b, complete with tongue poking the inside of her cheek and a faint frown at the corners of her lips. Twilight’s father had been rather bothered by his daughter’s relative impassive nature when growing up, and an instruction manual from the Canterlot Diplomatic Trainers section of the Royal Library had helped with calming his worries. With practice, making the correct visual response to questions had become almost second nature to her, although it was a little more difficult now.

“So, do you know you’re a changeling, Fluttershy?”

“No, I don’t think so.”

Twilight’s expression deepened into a 107c, Serious Consideration of Needing a Drink.

“So you’re not a changeling?”

“I suppose I could be.”

After a considerable amount time spent studying the hesitant pegasus/potential changeling, Twilight closed her eyes and rested a hoof on her forehead. “If you were a changeling, and I don’t think you are, I’m pretty sure you’d know it.”

“What if…” Fluttershy took a short breath and turned to look at Twilight Sparkle. For a moment, Twilight was almost afraid that her normal teal eyes would be the featureless blues of the changelings that had been kicked out of Canterlot just yesterday. “What if I didn’t know? What if the changelings stole the real Fluttershy away when she was just a foal and put a changeling in her place? Or what if Fluttershy actually died when she fell off Cloudsdale instead of being caught by a flock of butterflies? The changelings could have put the real Fluttershy’s memories into me and I might not even know! I could be some sort of secret agent of the changeling hive, sneaking away to report on my friends and betray Equestria while all along, the Fluttershy that you have known is really not even a pony! I don't think I could handle being a changeling! I mean I know you and the girls would still be my friends, but what would everypony else think? And what about all of my little animal friends? If I was a changeling, I would be feeding on their love to keep up my disguise. It could hurt them! Some of them might even… Twilight? What are—”

A stunning blast of magic swept over Fluttershy, making her pink mane stream behind her and a wave of crackling sparks dance across her cutie mark. After it passed, the only real difference between the yellow pegasus who stood there before and now was a severe need for a good brushing and a look of intense relief in those deep teal eyes.

“Changeling disguise removal spell,” explained Twilight Sparkle as she blew the dust from another book. “You’re you. As if there was ever any doubt.”

“Oh, thank you, Twilight!” The relieved pegasus moved up close to Twilight Sparkle and embraced her, with a little additional nuzzle afterwards. “You can’t believe how much better that makes me feel.”

“No problem,” said Twilight, dropping another book into a packing box. “That’s what friends are for.”