Author's Note

There's a part that's kinda gross so sorry 'bout that. It's not blood or anything it's just kind of gross if you think about it. But it goes by pretty quick, but it's mostly comedic. Just be warned.
I might just put it here:

"Weird. I feel like I could poop or pee at any moment even though I could control that when I was this age." Rainbow Dash answered. Sweetie Belle had a face that just said one word - "ew".

Comforting Scootaloo

Rainbow Dash flew through Ponyville looking for Scootaloo. She got a few odd looks but ignored it.
I'm sorry Scoots... she silently said, putting her hoof on her heart. I should've told you...
Why didn't she? Was she worried Scoots couldn't handle the truth? She was a strong filly, she could handle it! Or did Rainbow Dash just not think it was worth it?

She heard sobs and saw a green shield surrounding an orange pegasus filly and a white unicorn filly.
She flew down and landed in front of the shield.
"Scoots?" Rainbow Dash asked. "I don't know if you can hear me, but... Sigh... I'm sorry, okay? I should've told you. I don't know why. I guess I just thought that you knew already and that Cheerilee told you, but... I guess you deserve the truth. While I was at Junior Flight Camp, you were born. I came home to see you, and after a few years, me and Cheers were foalsitting you. We got into an argument and I got so angry I just took you away. I left you at Fluttershy's and a few months or days or weeks - I don't know how long - later Cheerilee took you home and... I couldn't stop feeling like a horrible sister. When I saw you for the first time I knew you were my sister and I was just acting too arrogant. I'm sorry. For everything."

Rainbow Dash didn't notice but she was crying with her eyes shut. She opened them and saw Scootaloo hugging her.
"It's okay..." there was an awkward pause, "sis."
Rainbow Dash wiped a tear away. Geez I haven't cried since I was a filly. Oh wait... I am one.
"Well let's get back to the others." Rainbow Dash said. She motioned to her back but Scootaloo reminded her that she was the smaller one. "Oh... right..."

So Scootaloo was giving Rainbow Dash and Sweetie Belle a ride back.
"So... What's it like being a filly again?" Sweetie Belle asked.
"Weird. I feel like I could poop or pee at any moment even though I could control that when I was this age." Rainbow Dash answered. Sweetie Belle had a face that just said one word - "ew".
"Yep." Rainbow said. "What's it like having your older sister be your younger sister?"
"Like you said, weird. I'm not even old enough to do, like, anything! I'm still a pre-teen!" Sweetie Belle exclaimed. "I can't take care of a filly!"
"She can take care of herself Sweets." Scootaloo said, looking back. "She has - at least somewhat - the mind of a mare."
"That's right - somewhat! She won't even be all the way matured until she gets her cutie mark..." she quickly added, "again."

Rainbow Dash nodded, before looking at her flank. Not having her cutie mark was weird. And she probably wouldn't have it for a few years, unless she somehow performed a Sonic Rainboom when she was, like... six.

"Ah hope Scoots is okay." Rainbow Dash heard Applejack say as they approached.
"Well," Rainbow Dash exclaimed as they flew in, "I'm okay! And she is too!"

"That's good!" Rarity exclaimed. "Apple Bloom said you three might go ask Cheerilee about letting us go to school."
"Okay! We'll go do that! C'mon guys!" Scootaloo exclaimed, flying out the window. Sweetie Belle and Apple Bloom followed.