it's simple, just do something impossible
Sunset Shimmer is six years old, her eyes are full of tears, and she is going to make a miracle.
There was a book she read once, one of the few fiction books she'd read that wasn’t missing a beginning, an end, or a middle. It was a book about a young colt named Little Bucket, and a very famous candymaker, and Sunset had liked it very much. Little Bucket, in particular, she had liked very much, because he had been hungry and tired and alone, just like her, and he'd held onto what little he had, and he made a miracle happen. A piece of chocolate that made all of his hopes and dreams come true and promised he would never go hungry again.
Standing next to the wrought-iron fence around Celestia's School for Gifted Unicorns, Sunset feels the magic in the air. It tickles her nose with the smell of impending thunderstorms, and prickles her fur with the feeling of the heat of the noonday sun, and runs through her horn like the burning impossibility of a surge about to happen. Out by the gates is a crowd of colts and fillies, each a year or two older than Sunset. They're all chattering and laughing, getting ready for the test to come. Sunset is in the shadows, around the side, and she’s suddenly happy that she's so skinny she'll be able to fit through the fence without getting stuck.
There was another book she read, that was by the same pony, that was missing a few more pages but that she still liked. This one was about a fox named Fantastic, and how clever and tricky he was. He went out and made miracles for himself too, sneaking around the mean griffons that kept trying to hunt him down so that he could steal food for his family. Sunset isn't Fantastic like he was, but she is still very clever. Sometimes she imagines that her coat is so yellowy-orange because secretly Fantastic is her dad somehow, and he'll show up in the dead of night with a bundle of carrots and a burrow down into a home where she'll never be cold again.
But he's a fox, and she's a pony, and she has to be Fantastic on her own. The gates open, and one by one the fillies and colts have their names taken down, and Sunset slips through when she spots a group of rowdy dirt-stained colts she might be able to blend in with. The more well-washed foals are avoiding them, but that's more of a benefit than anything, because she's heard noble foals say and do some very mean things, and heard worse rumors from the older fillies at the orphanage. She slips between the bars, and hangs a few hoofsteps back and to the right of the colts, and they don't notice her as they chatter but everypony else assumes that she's with them and where she needs to be.
Everypony is led inside to a very large ornate hallway and a large set of double doors. The mare with a clipboard in her aura yells a few times, and eventually all the foals have lined up along the wall of the hallway, and Sunset is barely listening because she can feel the thrum of powerful magical wards under her hooves and it’s wonderful. Then a name is called, and a foal from somewhere in the middle of the line gets up and walks through the door, and Sunset is worried. She is used to lines moving in order, not being called out by name, and her name definitely is not on the mare's checklist. She can feel her breaths beginning to get faster and faster before she remembers that the miracle was in Bucket's second candy bar, and that Fantastic had plans that went wrong, and she forces herself back under control so she doesn’t look like the filly two places down who's about to drop dead from fright. Sunset is not Fantastic yet, but she knows she can be, and she knows she has to be, and today she is going to make a miracle happen whether it wants to or not.
One by one the foals go in, and they don't come back out. Another exit to the room is Sunset's guess, even though she hears the colts on her right whispering about how if you fail the test Princess Celestia banishes you to the moon. Princess Celestia wouldn't do that. She’s a Princess. She has ponies to do that for her. One by one the hallway empties, and as it does Sunset slinks backwards into a slightly shadowed alcove. She's losing her cover of other foals, and she doesn't want the mare with the clipboard to drag her out by her ear. Finally, the hallway seems empty, and the mare looks at her checklist and then nods to herself. She walks into the room, and Sunset skitters from the shadows behind her to slip through the door as it closes. She loses a few tail hairs with a sharp tug of pain, but better that than getting stuck in the door. She only lets out a very small noise of pain, and none of the other ponies in the room notice her as she lurks in the entryway.
"That's all the foals who came," the mare with the clipboard says. Behind a large desk are two stallions and three mares, all much older than the mare with the clipboard. The mare in the center, a white unicorn mare with a very pretty pink mane, stretches herself and stands.
One of the other mares, a pegasus, turns to look at her. "Any notable..." she says, and the rest of the words are lost as Sunset sees her chance. The mare with the clipboard is busying herself picking up bits of paper-mache shell lying on the floor of the lecture hall, and the others are beginning to talk among themselves, and if Sunset can make it a few steps more she'll have her miracle.
Sunset canters up in front of the tall desk with all the ponies, and passes the mare with the clipboard and startles her badly, and says, "I am here to take the test!"
Conversation stops. Levitating bits of paper mache freeze in midair. The clipboard mare says, "What's your name, dear?"
"Sunset Shimmer," Sunset says. "I'm really good at magic. Give me the test."
"I don't see your name on here..." says the mare with the clipboard.
"Aren't you a little young for this school?" asks one of the stallions, an earth pony.
"I'm small for my age!" Sunset lies. "Give me the test."
The adults look at each other. The earth pony stallion says, "Miss," and seems to be about to say something else, but the mare in the center of the desk suddenly smiles, and walks around to Sunset, and kneels down.
She says, "Sunset, I'm very sorry, but we don't have any of the normal tests left. We only had enough for the fillies and colts we knew would be here. If you come back next--"
"Then give me a test that's not normal!" Sunset says.
The mare before her blinks, and opens her mouth, and then smiles a little wider and chuckles and says, "Alright little one, you've convinced me." The ponies at the desk whisper to each other, and the mare with the clipboard looks shocked, but the white unicorn with the pink mane lights her horn up with the color of a bright summer morning and casts her vision around the room and smiles. A small rock sitting on a shelf lights up and floats over to land in front of Sunset, and she examines it. "This is a phoenix egg," says the mare with the pink mane.
"This is a rock that somepony has painted red," Sunset says, brow furrowing. She thinks suddenly that the mare is making fun of her, and resolves to do all the better on the test for it.
"That's what's so clever about phoenixes," the mare with the pink mane says. "They lay eggs which look like ordinary rocks so that most ponies never look twice at them, but if you know what you're looking for, you can see the incredible potential it has." The ponies at the desk are whispering more now. Sunset stares down at the rock, weighing the odds of that being true in her mind.
"Your test," says the mare with the pink mane, "Is to hatch the egg. Do that, and I'll admit you to the school." And just like that, the truth ceases to matter. The mare has given her a goal, a way forward. Hatch the egg, and that will be your miracle, and so it doesn't matter what the egg is because whatever it is Sunset Shimmer is going to hatch it.
So Sunset screws up her courage and her magic and her soul and pours everything into her horn. Her magic encapsulates the egg and pierces it deep, layering itself through and inside it, and it feels like a rock coated in paint but Sunset Shimmer knows better, now. This isn't a rock. This is her miracle, and she just has to tell it so. The magic around Sunset's horn redoubles, triples, and the mare with the pink mane takes a step back, mouth open, but Sunset isn't going to stop because this is her test.
The room begins to rattle. The other ponies start to sweat. Froth is forming on Sunset's coat. Someone cries out, far away in the distance. She thinks they're telling her to stop, but the egg is gleaming gold now. The color of a miracle.
A burst of power shakes the room and shatters the windows and sends Sunset tumbling into the mare with the clipboard. The ponies are cowering behind the desk. The mare with the pink mane is wearing an expression of pure shock. The egg sits in the center of a crater, untouched.
"Sunset," begins the mare with the pink mane. Her face is creased with worry. Sunset raises a weak hoof, and she cuts off. Sunset points to the egg, and the mare stares. There's a cracking noise. A chip appears in the egg. Then another. And then, with a burst of flame, a tiny phoenix chick leaps from the shell and soars a beautiful glowing trail in the air and lands on Sunset's head. The mare with the pink mane wavers, shock evident on her face. Her form wavers, and shifts, and melts away like candle wax to reveal the towering form of Princess Celestia herself.
"I passed," Sunset tells the most powerful creature in Equestria. Then, Sunset's vision goes black, and she knows no more.