The next day, Starswirl was doing what he usually did when he wasn't working on the portal, teaching his apprentices.
"Al, you have to focus," Starswirl instructed. "You'll never get good at this if you don't have focus." Al groaned. He had heard this a lot. Just then, Harmony walked into the room.
"Hey, Starswirl?" Harmony asked. Starswirl turned around to face Harmony.
"No, Harmony, I haven't finished the portal yet." Starswirl sighed, annoyed.
"No, no." Harmony waved the statement away. "I was just asking about a time travel spell." If Al was taking a drink, he would have spit took.
"There's a time travel spell?!?" Al screeched in surprise.
"Yes, well," Starswirl was going to say.
"Why haven't you used it to stop Celaria, from starting this whole thing in the first place?" Harmony asked passive-aggressively. Starswirl noticed this and adjusted his tone of speech accordingly.
"Al, Clover," He said to his apprentices. "Please leave us to speak in private. Both the apprentices left the room. Then, Starswirl addressed Harmony. "Because of the resulting time paradox." Starswirl responded, matter-of-factly. "It would rip apart our world, and yours as well. Or, at the very least, remove us from existence."
"What a load," Harmony replied, unbelieving. "Just do it." Starswirl sighed at the request and began to explain why it was a REALLY bad idea.
"If I went back in time to stop Celaria from bringing you here, then she wouldn't." Harmony was about to speak, but was silenced by Starswirl. "SO, you would never live here, up to the moment you tell me to go back and change the event, the only reason I do so. SO since I never go back and change the event, Celaria does go get you, and you do live up to this moment, and I do go back and change it, and the cycle repeats forever, creating a paradox." Harmony fell silent. "It get's worse. The timeline would seek to solve the unending paradox, and the only way to do so, is to remove all involved in the paradox from existence, namely you, me, and Celaria. After that, the timeline would adjust itself and move everypony related to us around so that they were in a way in which they never met us, meaning the young princesses would be gone as well." Starswirl finished his explanation, and Harmony was wide-eyed as well as against the idea. Harmony opened his mouth to say something in opposition, but was silent when he realized his argument was mute.
'How can I argue against that?!?' Harmony thought to himself. Starswirl grinned at his minor debate victory.
"Thank you for the debate Harmony, I do enjoy a debate, now I must get back to work, so you can go now." Starswirl shooed Harmony away, picking him up with his magic and gently setting him down outside the door, closing it behind him.
Harmony was lying on his back on the palace lawns, staring up at the sky and pondering anyway he could (and even if he was ever gonna,) get home. He lifted his hooves up to his face and sighed. He hated them. He wasn't even sure why, he held nothing against his hooves or pony body, in general. Harmony lowered his hooves back to his sides. He closed his eyes.
'On the bright side, at least I didn't get stuck in Fallout.' Harmony thought to himself. Then, Luna walked up.
"Hi, Harmony!" She said, as excited as always to see her big brother. Harmony wasn't planning to stay in Equestria forever, and some part of Luna knew this, but that part denied it anyway. So, for all it was worth to Luna, Harmony was her big brother. Harmony opened his eyes and looked at her. It took him a moment to register Luna, because (in his perspective) Luna was upside down, standing on a ceiling of grass above an infinite blue abyss that was the sky.
"Oh, hi Wuna." Harmony had taken to calling her "Wuna" because of the way she pronounced her name a year ago. Luna groaned. She hated that name.
"What are you up to?" Luna asked, laying down on her legs next to Harmony. Luna, had the mind of a 12-year-old, a shy, 12-year-old.
"Oh, nothing really. Just thinking." Harmony said to Luna.
"About Earth?" Luna asked. Harmony nodded.
"Yeah," Harmony said, longingly. After a moment, Luna said something.
"Can you tell me about it?" Luna asked. Harmony looked at Luna, surprised.
"S- sure," Harmony said, caught off guard. "I'll tell you a bit about Earth."
And so he did.
Harmony told Luna the best of humanity. And she loved it.