(I am currently working on a new version with an editor but I'm leaving this one up as it's already on peoples bookshelf)
Sunny Starscout was walking around Maretime Bay still overjoyed at the fact that all pony races were together again. As the sun began to set, she walked home to her newly rebuilt lighthouse. As she entered, she smiles turning and looking at her father's picture on the wall 'we did it dad' she thought to herself. Sunny walked to the kitchen grabbing an apple and eating it. Sunny then walked to her bedroom as she continued eating her apple. She had been worn out by the days' events's not to mention the wings and horn don't help. Sunny still wasn't sure if it would be a permanent change. As she enters her room, she notices that her box of Twilight and her friends was missing Twilight. "That's strange I was sure I found them all especially Twilight Sparkle" As she began searching for her lost Twilight, she heard a loud noise from the lighthouse above. As Sunny quickly made it to the elevator and up to the lighthouse lamp room, she saw what had made the noise. Sunny stood silently at the figure in front of her. She had never seen a pony so tall, but she soon noticed the pony's cutie mark. As she gasped and tripping over her own hoofs and landing on her rump, the pony turned around to face her after hearing the commotion.
“Oh, I’m sorry my little pony, I didn’t mean to scare you” the mare walked over holding out a hoof to help Sunny up
Sunny took the mysteries pony's hoof to stand up "Princess Celestia?" Sunny asked
The mare looked surprised before smiling “I’m surprised you know who I am young mare”
Sunny quickly grabbed her book “of course I do you were Twilight’s mentor and teacher. You’re also a princess of Equestria! I have so many questions for you!”
But before she could say anything else Celestia interrupted “I’ll answer your questions my dear but who are you?”
Sunny blushed red from embarrassment realizing she had been so caught up with the fact Celestia was here that she didn’t even introduce herself to the sun princess. “I’m Sunny… Sunny Starscout.”
Celestia smiles looking at Sunny and seeing the same spirit she saw in Twilight. “Well, it’s nice to meet you, Sunny.” She looks around herself before noticing the artifacts from her time “Are these yours Sunny?”
Sunny smiles “well they were my dad’s. He told me so many stories when I was a filly about when Twilight and her friends. How they were all so different but friends. That they changed Equestria for the better even that they saved your sister from Nightmare moon”
Celestia smiled remembering when they returned Luna to her. How they saved Equestria so many times. Her ears droop slightly before speaking “Yes indeed, Twilight and her friends saved Equestria too many times to counts." She smiles slightly "now what questions do you have young one?"
Sunny didn’t notice the slight change in her ears. “Well, why didn’t you come back and help us?”
Celestia knew that was going to be asked at some point "well sunny, I didn't know. I and Luna have been traveling the world for so long now it never occurred to us that Equestria was in trouble”
Sunny nods taking notes "what happened to princess Twilight and her friends?"
Celestia sighs “Twilight I do not know as being an Alicorn should extend your life almost forever. Spike is probably in a cave somewhere. As for the others as like most ponies they passed on”
Sunny nods writing even more notes “Why did the crystals give me a horn and wings?”
Celestia study the pony for a moment before answering "my best guess is that's what's left of Twilight's magic. A fail-safe in case she failed the magic of friendship"
Sunny looks for a second surprised by the answer before writing down what Celestia said. She paused so many questions running through her mind. But before she could ask another question Celestia spoke.
"You remind me a lot of Twilight before I left. You are very curious and observant. You value your friendship not only within your race but in all the pony races. My dear Sunny it seems to me that you're exactly the pony who can mend the troubles between ponykind and the other species of this world. Never lose yourself." She paused for just a second breaking down some "I failed Twilight if she needed help, I should have returned but I didn’t. I hate to imagine her feeling of loss when her friends died. Maybe that when she disappeared or whatever happened to my student." She hands Sunny the Twilight figure that had disappeared "you are the future of Equestria my dear Sunny. You and your friends will make Equestria a better place like back in the days of Twilight Sparkle and her friends. Don’t ever give up no matter how bleak it looks”
Sunny nods no longer taking down notes. She was far too entranced by what Celestia was saying. She quickly snapped out of it "yes Princess" it went silent for a few minutes before Sunny spoke up “Can I hear more about Twilight and you?”
Celestia smiles “yes but it’s quite a long story…. Long ago….”
A couple of hours later
“The end” Celestia smiles as she sees the wonder and aww in Sunny’s eyes
“That was so amazing” Sunny looked at her Twilight figure “she’s so amazing and so are you!” she smiles
Celestia smiles sweetly “Thank you my little pony for listing to this old mare” she looked out the window noticing the moon was close to setting “well Sunny it’s time for me to depart”
Sunny looked at her slightly disappointed “It was so nice meeting the mentor of Twilight.” She hugs Celestia and Celestia returns the hug
Celestia smiles “don’t be disappointed Sunny, we'll meet again someday." Celestia uses her magic to open the door at the top of the lighthouse letting go of Sunny and flying away.
Sunny waves goodbye as she looks around, she sees that Celestia left a white feather from her wings. Sunny picks it up and sets it beside the purple one her dad had collected. Sunny then heads downstairs crawling into bed before closing her eyes she smiles "Thank you princess Celestia" she closed her eyes drifting off to sleep. A few hours later there's a knock at the door. Sunny groans getting up as she opens the door she smiles seeing her friends there.
Hitch laughs “morning bed head”
Sunny smiles before letting them all in “I met princess Celestia and I have a lot to tell all of you” she smiled looking at her four friends who are confused and excited to hear what Sunny had to say. Sunny smiles “it all started A long long time ago……”