Why would Lyra lie about her age? Pinkie wondered as she ran home. What could be so important about her age that she'd have to lie multiple times? Her thoughts to Vinyl Scratch. Pinkie had remarked she had looked young, and Vinyl had looked- scared.

Pinkie instantly had a theory- a crazy, insane, incredible theory. There was a possibility that Lyra and Vinyl were-

"Immortal," Pinkie stated aloud. "They're immortal."

Pinkie's friends had changed over time. Rarity's hair was a paler shade of white, Applejack had circles under her eyes all the time, and Fluttershy's hair grew out really long. But now, thinking about it, Pinkie realized Lyra and Vinyl had always looked the same. They didn't look a day over twenty.

"Gummy!" She called to her pet alligator, who was lying in a water trough outside the house. "I need you to call Angel, Owliscious, and all the other pets! I need to tell the girls something important. It can't wait! And I need to tell them all at once!" She pulled Gummy out of the trough. Gummy began walking away, to the library. Pinkie smiled after him.

"Buttercream! Lucky Clover!" She called, opening the door. "Does anypony want peaches?"

~

That night, when Pinkie left to the library, the sky was dark. Despite the humid air, Pinkie shivered in the gloom.

"Twilight!" She called softly, knocking on the library door. The door's handle turned, and Pinkie was let in by her friend.

"Hi, Pinkie!" Twilight greeted her from her loft. "Fluttershy's in the gardening section. How's life?"

"Awesome!" Pinkie exclaimed. "I have something really important to tell you guys."

"Ah," Twilight replied knowingly. "When's the due date?" Pinkie giggled.

"No, silly! I'm not going to have another foal!" She answered. Twilight looked disappointed.

"Well, I could've foalsat while Glimmer Wave was staying with Comet Tail's parents," she replied. "They left this morning."

"Really?" Fluttershy asked from the next room. "I thought they weren't going for another week." She entered into the main room. Twilight shook her head.

"Comet's parents are distant royalty, and they wanted to introduce her to royal life."

"She's a princess, though, isn't she? And you too, right?" Pinkie asked.

"I'm only a princess by marriage. Glimmer is the princess by birth. Still, it's not like she'd inherit the throne or anything."

"Such a pity," Rarity remarked from the doorway. "Glimmer Wave would make excellent royalty."

"Rarity!" Pinkie exclaimed, running up to hug her. Rarity hugged her back.

"It's been too long," she remarked. "Anyway, I hope this doesn't run on too long. I left Rising and Brilliance at the boutique, and it just might be in shambles when I return." The four girls laughed.

Knock! Knock! Knock! Twilight opened the door with her magic, and into the room stepped Applejack.

"Howdy, Twi, Rarity, Fluttershy, Pinkie," she greeted them.

"Hello, Applejack," Fluttershy replied.

"Hi!" Pinkie exclaimed. Thunder rumbled, and Rainbow Dash flew into the room, wearing her Wonderbolt Flight Suit.

"Hi, Dashie!" Pinkie exclaimed. She and Rainbow Dash high-hoofed.

"What's on the agenda, Pinkie?" Rainbow asked.

"Yeah, I'm curious," Twilight admitted.

"Me too," Fluttershy added quietly. Pinkie looked around the room.

"Weeeeeeeeell," she began, taking a deep breath. "I think Vinyl Scratch and Lyra Heartstrings are immortal." The room went dead silent. Even Rainbow Dash's wings stopped beating.

"Guys, we need to call the doctor," Rainbow Dash joked. "Pinkie Pie has officially lost her mind. And there's no getting it back." She laughed. Rarity and Applejack joined in.

"Pinkie, be reasonable," Twilight told her logically. "The only immortals are alicorns like Princess Celestia." Pinkie stomped her hoof.

"It's possible!" She exclaimed. "And I'm gonna prove it!" That made Rainbow Dash laugh even harder.

"I have to tell Northern Spark that Auntie Pinkie's gone 20% nuttier," she exclaimed, then flew out. Her laughs echoed behind, like past memories fading away.

"Quite a theory," Applejack commented. "What's next, Mystery Mint is secretly Rose?" She laughed again and trotted out. Rarity left, muttering to herself about too much cake.

"Why won't you give me a chance?" Pinkie asked, following Rarity and Applejack out of the library. "Wait!"

"I believe you, Pinkie," Fluttershy said quietly, coming out behind her. Pinkie swiveled around.

"Really?" She asked hopefully.

"Well, nothing impossible," Fluttershy remarked, fiddling with a strand of her long hair. "So, why not?" Pinkie hugged her.

"Oh, thank you!" She exclaimed. "We'll prove it tomorrow morning!"

"T-tomorrow morning?" Fluttershy squeaked. "Oh my..." Pinkie waved and skipped away. The rain began to fall, but Pinkie didn't mind. She was excited at the prospect of a mystery.

Mystery isn't the word for it, Pinkie decided. Maybe, challenge is better?

"Yeah," she agreed with herself. "Much better."

Author's Note

I have now decided this is an AU.