It was a nice day outside, and Sunset Shimmer had decided to take a break from being inside to look around. For two weeks she had difficulty talking to anypony because two weeks ago her brother had gone missing. And it's been difficult for her to connect to anyone else.

As she explored outside however, she soon heard Princess Cadence with a young foal. Checking it out, Sunset found a purple unicorn filly.

"Oh hey Sunset. I guess you found me doing my foal sitting job." Cadence said.

"Foal sitting?" Sunset asked.

"Do you know Princess Cadence?" The young filly. "She's the best foal sitter ever!" She said. The way the young filly said that just melted Sunset's heart.

"You could say that. Got a name, kid?" Sunset asked.

"My name's Twilight Sparkle. And you are?" Twilight asked.

"I go by Sunset Shimmer." Sunset said. Suddenly Shining Armor showed up.

"Oh hey Sunset. I see you've met my baby sister." Shining Armor said.

"Captain Shining Armor is your brother? That's actually pretty neat." Sunset said. Then she had a thought. "You know, Captain Shining Armor is a cool big brother and all, but do you have any big sisters in your life?" Sunset asked.

"Nope. All I have is Shining Armor; he's my B.B.B.F.F.!" Twilight said.

"B.B.B.F.F.?" Sunset said confused.

"Big Brother Best Friend Forever. It's a thing she does." Cadence said. That sealed it for Sunset.

"Well then, even if we're not blood realtives, I think I can be a good big sister model for you Twilight. What do you say; would you like me as a surrogate big sister?" Sunset asked.

"What's a sere-gat?" Twilight asked Cadence. Sunset couldn't help but shake her head and smile.

"She's young but she tries..." Cadence said. "Twilight, a Surrogate is the same as a substitute." She answered Twilight.

"Oh! I know what a substitute is! Okay Sunset, you can be my substitute big sister if you want." Twilight said. "Is that something for roleplay?" She asked. Shining facehoofed but Sunset just got down on Twilight's eye level.

"Not really. Basically, I'm going to hang out with you and help you out where you need it kid. Anything you want, I'll see if I can help you out with it. In other words, this is going beyond simple role playing." Sunset explained.

"Oh...I thought you meant you'd play with me." Twilight said.

"Do you want me to play with you right now?" Sunset asked.

"I'd love it if you'd play with me." Twilight said.

"Then what do you want to play, Twilight?" Sunset asked.

"Let's play tag." Twilight said before booping Sunset's nose. "Your it!" Twilight said before running off. Sunset couldn't help but laugh.

"Hey! Wait up!" Sunset said before chasing after Twilight.

"...Shining, you look worried. Is it because of Sunset's attitude lately?" Cadence asked.

"Something like that but..." Shining said. "I can't bring myself to object and now seeing Sunset interact with my baby sister...maybe this is for the best for both of them. Twilight doesn't have any friends outside of me, and I think Sunset could use someone to mentor." He explained. "It'd help her get over...you-know-who..." Shining added.

"I get what you mean. Plus, Twilight seems to really like her." Cadence said.

Later on, the sun began to set.

"Gee, you've got a lot of energy in you kid." Sunset said. "Unfortunately I gotta go for now. I'll hang out as often as I can though. And if you ever need me for anything, give the message to your brother, but only for an emergency." She said.

"I understand. It was nice of you to play with me Sunset. Thanks for today." Twilight said. Sunset smiled and left back towards the castle. She didn't even know that Celestia had watched her the entire day.

"So that purple unicorn actually melted Sunset's colding heart...how interesting." Celestia said. "I suppose I won't have to show her the mirror after all." She added before heading back inside.

A bit later as night approuched, Sunset started to get in bed.

"That Twilight Sparkle...something about her reminds me so much of my baby brother. Wherever he is, I hope he's okay. For now, I'll do for Twilight what I couldn't do for my baby brother." Sunset said before laying down. "Goodnight Twilight...I hope someday you can call me your B.S.B.F.F.; short for Big Sister Best Friend Forever..." She added before falling asleep. She didn't know that Celestia had heard her lament.

"...This Twilight Sparkle...whoever she is...seems to be a good influence for Sunset. But I have no idea if this was a one day thing..." Celestia said to herself.

Over the course of the next few weeks let alone months, Sunset's attitude had improved greatly and whenever the orange unicorn could, she was hanging out with her new surrogate little sister, thus proving that it wasn't a one day thing. It didn't take long before Twilight began seeing Sunset as her big sister, and even once called her B.S.B.F.F. and as far as Shining was concerned, he was happy that Sunset could become the big sister Twilight needed. Not the big sister that Twilight could have wanted, but the big sister Twilight needed to have in her life.

And one day, when Cadence revealed to Twilight that Sunset was in Celestia's School for gifted unicorns, the purple unicorn wanted Sunset to teach the young filly some magic. Sunset was more then happy to oblige and soon enough, the two were growing close together.

When Twilight decided she wanted to attend the school as well after that year's summer sun celebration, Sunset used her position as Celestia's student to speed up the application approval by a whole week, and the approval was given within just three days! The day of the test, Twilight began to feel nervous.

"I'm scared big sis..." Twilight told Sunset.

"You'll be fine. Just go in there, do everything I've been teaching you, and you'll nail the entrance exam no problem." Sunset said. But then the test got changed on them both: Twilight had to hatch a dragon egg. Which pissed Sunset off. What is Celestia thinking? Foals Twilight's age can't hatch this; only an Alicorn could harness enough magic to hatch this... She thought to herself. While most of her greed and ambition was nulled by Twilight, Sunset wasn't okay with many of the things Celestia was doing as the Princess of Equestria.

And just when it looked like Twilight had flunk her entrance exam, suddenly a big rainbow explosion jump started Twilight's Magic to the point where her magic had to be reigned in by Celestia. Thankfully, not only did Celestia forgive Twilight's actions, Twilight had successfully hatched the Dragon Egg. Not only that, but Twilight even got her cutie mark that day. Once it was revealed, Sunset gave her little sister a big hug.

"You did good little sis. You did good." Sunset said. "And you couldn't have made me prouder." She added.

"Now Twilight Sparkle was it? With that much magical power in you, I think I would like you to personally study under me alongside Sunset Shimmer here." Celestia said.

"Wait Sunset...you never told me you were the Princess's personal student." Twilight said.

"Didn't want you to think any different of me. I wanted you to treat me like you would any one else that came up to you." Sunset said.

"Oh. I think I get it. I forgive you, B.S.B.F.F." Twilight said, smiling.

"Thanks L.S.B.F.F." Sunset said. Celestia couldn't help but smile. Just a few months ago, Sunset wouldn't have done something like this. But whatever it is about Twilight, it's made Sunset change for the better. That's why Celestia is sure about this decision.

"But before we wrap up here...Princess Celestia, I would normally never question you, but seriously? HATCHING A DRAGON EGG? WHAT WERE YOU THINKING?!" Sunset asked, practically yelling.

"That was not my decision. And as for the pony that is responsible..." Celestia said. That's when everyone noticed that one of the judges had tried to sneak off only to be caught by Celestia. "...I thought I warned you that the next time you did something like this, you'd be fired. Well, apperently words aren't enough. Pack your things for tomorrow, because as of this moment, you are FIRED!" Celestia said before throwing the pony out of the room.

"...Oh...never mind..." Sunset said, feeling guilty for accusing the Princess of this.

"It's fine, Sunset. I don't blame you for thinking I was responsible. And I am partially responsible. I'll have to have that judge replaced for this." Celestia said and left.

"Why'd you go off on Princess Celestia for that, Sunset?" Twilight asked.

"Twilight, I've witnessed the princess making a lot of controversial decisions. It's gotten to the point where I'm getting fed up with the ones that are just plain stupid." Sunset said. "She's lucky this wasn't her fault this time." She added before leaving.

"...There's a history there...but my big sis will tell me when she's ready." Twilight said. She had no idea how long it would be before she found out about said history.

Author's Note

Enter my new alternate universe, where Sunset becomes an Element of Harmony and meets Twilight before the purple unicorn enters Celestia's School. Who is Sunset's Brother, and what his disappearance have to do with how Sunset went off on Celestia? Stay tuned for more info!