"You think you already know me. Well you could be right. Or are you... I remember my heroic duties in the past, ever since Princess Twilight came to Canterlot High, me and my friends were gifted with equestrian magic for magic, and we used it to defeat who will become our friend, Sunset Shimmer. Than after, Sunset Shimmer redeemed by reminding us they we were all friends when saved the school from the sirens known as the Dazzlings. We all transferred our magic to Sunset when she helped the Twilight of our world free herself from the monster she was turned into during the friendship games. And we all pitched together and accepted our superpowers and became superheroes to freed everyone from Camp Everfree. And ever since then... Me and my friends have accepted our fates of being superheroes. We even dealt with lower enemies, like Wallflower Blush and Juniper Montage. And recently we accepted out fates as being superheroes when we took on a creazy monster named Kavitor. My name is Rainbow Dash. And this is my story of how I became... An official superhero for freedom, friendship and justice."
A few days after the events of Spiders and Magic Equestria Girls...
One day at Canterlot High, Rainbow Dash gather all her friends to make an important announcement. "Gather around girls. Gather around." She said.
"What is it Rainbow Dash?" Sunset Shimmer asked. "It better be important."
"Of course it's important. As you all know. We have accepted our roles as Canterlot City's mightiest superheroes." Rainbow said.
"Yeah we know. We fought that giant robot toaster gone bad." Applejack said.
"And we posed heroically." Pinkie Pie said.
"Good times..."
"Lets not forget that monster we fought last week, Kavitor. He was intense." Fluttershy said.
"Well I am planning to become a superhero without ponying up." Rainbow Dash said. "What do you think?"
"Really? How?" Fluttershy asked.
"I still have my super speed, so I'll be speed themed superhero." Rainbow replied. "I've been practicing on my speed a lot when I got home. And it would be awesome to be a for real life superhero, patrolling the city, fighting crime, and bring peace."
"Darling. What's wrong with our pony forms?" Rarity asked. Don't you like your pony ears and wings?"
"Don't get me wrong. I like my pony form. I'll keep it as a last minute transformation. But I'll mostly use it for when we take on a main threat. Besides, there's a while world out there, full of evil, full of people crying out for a hero. And I'm gonna be one of them. I can protect the world." Rainbow Dash said. "Well sorta speak.
"Rainbow, I know I have accepted the fact that we are superheroes. But we don't need to be daily. We're still normal teenage girls. We can be superheroes when threats like Spot, or Kavitor appear." Twilight Sparkle pointed out.
"Twilight, trust me. I know what I'm doing. Our battle with Kavitor opened my eyes. When I look at this room, I don't see normal girls. I see potential. We could all be our own superheroes." Rainbow said.
"Ah was gonna join the firefighter team so I can help them open hydrants to they can get the water easily." Applejack said.
"I was thinking of moving to the Forrest to become an animal guardian." Fluttershy said.
"A firefighter, an animal protector, those are just normal hero stuff. Look, I even have my own costume." Rainbow opened her bag and in it was a Halloween costume she bought from a store.
"See?"
The girls started to laugh. "That's silly Rainbow Dash, since when is pink your color?" Pinkie Pie said.
"That's really is silly." Applejack said while laughing.
Rainbow Dash looked closely at her costume. "Oops." I must've mistakes it for blue." Rainbow Dash quickly changed out of her costume and felt embarrassed.
"Listen Rainbow Dash. It's up to you if you want to be a costumed hero. But we're not interested. We are all going our seperate ways to find our place in this world now that we are superheroes." Sunset said.
"Fine. I can be a superhero. And I know just the perfect outfit. My hair is colorful enough. I'll show you all next week." Rainbow said. "Toodles." She left to figure out what could she wear to start her job as a crime fighter. She has her speed, she has dashing good looks. And she's energetic.
Later, Rainbow Dash was practicing her speed on a treadmill, then She went to a local gym and lifted a few weights for her arms and legs to give them a little boost. She boxed on a sandbag to give her a boost in fighting with her hands. And she is already a black belt in karate so she feels prepared for whatever comes her way.
She went online and bought a white woolly onesie with a white hat and some white gloves and to see what she would look like. She put some white socks on but shoes. She looked at herself in the mirror and realized what she made of herself. 
"I look so cool. I may need a mask, not too simple, a red one, they would consider me a vigilante. I'll look so awesome as a superhero. Tomorrow I'll test out my speed with my official supersuit and then I'll start my new life of being a superhero. This is going to be awesome. I don't think I'll need a name for myself. Everyone was use to me with magic, I'll just call myself...Sonic Rainboom, the fasted girl alive." She said.
Rainbow Dash keoted her suit on as she goes to sleep to get ready for the morning. She was finally going to get her wish of being her very own superhero. She dreams of fighting armed robbers, ninjas, and supervillains that want to take over the world. But she'll have to make sure she won't get to exited about fighting a supervillain, and she should not get to overly excited or else she will be taken down easily, and sometimes being a superhero is not always going to be easy. But what ever comes her way, she'll see it though.
To be continued...