"Right! It's a long shot, but I think I can get you back to your universe." The Doctor was pacing back and forth in front of the throne, on which the princess sat, eyes following his movement. The Doctor's two companions stood to the side. Ditzy was seemingly relaxed, but River could see the stress riding in her back. She rubbed her cheek against the other pony's mane, and Ditzy threw her a grateful look.
The Doctor stopped short and wheeled around. "River, Ditzy, you two are going to have to pilot the TARDIS by yourselves. I'm going to be busy." The two nodded in unison.
"If only you had a full crew, sweetie," River laughed, trying to lighten the mood. The Doctor smiled, but once again it didn't reach his eyes.
"How many does it take to crew your ship, Doctor?" Celestia asked, oblivious.
"One," the Doctor said, just as River said "Six." Celestia smiled down puzzledly. The Doctor shot River an evil look. "Six to man her properly. But I do just fine on my own."
"Oh, please. I feel like we're crashing every time you fly her."
"River you're just rude. Don't you bad mouth my driving."
"No, it scares me too," Ditzy mumbled. River threw a foreleg around her.
"See? If you would just listen to me every once in a while."
"Are you saying you know my ship better than I do?"
River started to answer smugly, but the princess interrupted suddenly.
"Doctor, I know six ponies who would love to crew your ship." She gazed at a window with a knowing smile on her face. The three smaller ponies stared up at her, slightly bemused.
"Princess, with all due respect, this isn't an adventure for just anyone," said the Doctor.
The princess turned her eyes to him slowly. "Oh, but Doctor, these aren't just any little fillies. They're the most powerful force I have in Equestria."
Before the Doctor could open his mouth, a gray unicorn guard burst through the door at the end of the hall. He galloped up before the throne and bowed, out of breath.
"Princess, I'm sorry to interrupt," he panted. "But the Elements have come looking for you."
The Princess smiled down at him kindly. "Thank you, Ferrius. Please fetch them." The guard started to gallop off. "At a comfortable pace!" she yelled happily. She turned her attention back to the Doctor. "You will get to meet them very soon, I believe."
"But princess, I can't just take any random pony on my ship. It's just not – "
But the Doctor was cut off once again by the opening of the chamber doors. River felt a shiver of premonition as the princess announced "Doctor, I would like to introduce you to the Elements of Harmony."
River and the other two ponies turned to see the most powerful force in Equestria. To her shock, she was met with the sight of the five ponies she had met before, plus another unicorn, white with a purple mane. At the head was Twilight Sparkle, whose eyes narrowed when she saw River.
"You," River heard her breathe; barely audible as she felt a piece of time click into place. A light began to glow on Twilight's horn, and with a loud pop the unicorn disappeared. The other five newcomers glanced at each other awkwardly, and then set their sights on River. They glared at her, save for Fluttershy, who River doubted could glare, and Pinkie Pie, who smiled happily at River.
"No, Twilight, it's quite fine." River heard the princess say. Cautiously, she turned, and was surprised to see the purple unicorn beside Celestia. Teleportation, River thought. The Doctor smiled widely at her, clearly impressed by this skill as well.
Twilight muttered something else to Celestia, who simply shook her head. Twilight threw River a nervous glance, but she did not argue with her princess. She bowed her head as the princess rose, and a noise from behind told River that the other five ponies were doing the same.
"Girls," Celestia began, eyes trained on the Elements. "I'm so glad you've come to see me. But, unfortunately, your problem must be set aside for one that's a great deal larger." Her face grew grave as she studied all of the ponies in front of her. "The Doctor here can help, but only with your assistance can this plan be completed. Will you help me?" At this she turned to Twilight Sparkle, who was sitting on her right side. The younger pony held the princess's gaze for a beat, and then slowly nodded.
"Of course we'll help you, Princess." Though the words had come reluctantly, River could tell they were honest. I wonder what their story is, River thought to herself, knowing the connection between the princess and the unicorn was much deeper than it seemed.
"Excuse me, but… uhm… I'm sorry… but we don't really know… what… umm… this plan is." Fluttershy's tiny voice barely carried across the throne room, and it only got softer once she realized everypony was staring at her. The other four grouped around her looked at her like they had elected her to speak for them. River wondered why, as Fluttershy seemed to be the worst candidate for the task.
Celestia smiled gently at the cowering pegasus. "I'll explain on the way, my little ponies."
River wasn't entirely sure how all of them had squeezed onto the chariot, but it was relatively comfortable, even with nine regular sized ponies and one large alicorn onboard. She raised an eyebrow at the Doctor, who smiled gleefully.
"Bigger on the inside! Who knew?" He laughed and patted Ditzy on the back. The pegasus was staring ahead, pointedly ignoring the chariot pullers. Celestia was informing the Elements on the details, and while most of them were rapt with her, Twilight kept one judgmental eye on River. River stared back for a bit until Celestia's hair moved, blocking her view. The Doctor was seemingly oblivious to the exchange, smiling mildly.
Ditzy caught his attention, asking, "Why is she explaining it so… weirdly?" River listened in for a moment, and realized the princess was giving a very skewed, simplified version of her story. "Does she think they aren't smart enough to understand?"
The Doctor shrugged, patting her again. "Maybe, or maybe – "
"She's softening it for them, doesn't want to risk a shock." River interrupted.
"Right, I was going to say that."
River rolled her eyes at the Doctor. Ditzy looked more confused than usual.
"But I understood. I understood everything," she looked down at her hooves. "Well… almost everything."
"It's because she knows you're clever!" the Doctor told Ditzy happily. The pegasus beamed up at him, a smile so infectious that River had to join.
By the time they reached Ponyville, it was almost dusk. Celestia looked up at the rising moon, as though making sure it was still there. Twilight Sparkle rubbed her cheek against Celestia's foreleg, and the princess looked down at the unicorn. A sad smile passed between the two.
"Don't worry, Princess, I'm sure Luna will be okay until we come back." The pair turned their gaze back to the sky.
"I just hope she's up to moving the sun and the moon…" Celestia murmured.
River's eyes bulged as she looked at the Doctor. He smiled a little at her.
"This planet doesn't rotate. So Celestia and Luna move the sun and the moon, and the pegasi move the clouds. It's interesting, really. Done all through psionics and manpower… er… pony-power."
River filed that in her brain under something to come to terms with later, a pile of information that seemed to be growing by the second.
"Right!" the Doctor called, drawing all attention to himself. "I think it's time that I introduce you all to the TARDIS."