Spectrology

It was a sunny day in Ponyville, albeit windy. Rainbow's friends were listening to her newfound discovery about why corkscrewing reverse loops don't really work. Of course, Twilight already knew, and made sure to make Rainbow Dash aware of this at regular intervals. A waiter came and they ordered six milkshakes of varying flavours, which they thankfully didn't have to wait long for.

While the rest of them slurped milkshake, Twilight begun a technical explanation about why exactly corkscrewing loops don't work. Rainbow cut her off.

“Yeah, yeah, because lift and roll gives a barrel roll. I realised. Mid-loop and upside down.”

Twilight raised an eyebrow. “That can't have ended well.”

Rainbow half-grinned sheepishly. “Let's just say I'm stuck without flying for a day or two."

The others shared an “ouch” and a sympathetic frown, and Rainbow reassured Fluttershy that, no, it didn't hurt that badly.

“Need a place to crash? I can fix up the guest room,” Applejack offered. Rainbow put on a smirk and waggled her eyebrows, and a flustered Applejack continued, “You know what I meant.”

“Yeah, thanks, AJ,” Rainbow chuckled.

Rarity rolled her eyes. “Anything at all we can do to help, you let us know, okay? Maybe a spa visit for your sore muscles?”

"Thanks, but I just need some rest." Rainbow frowned at the word; Resting was almost as boring as a trip to the spa.

Pinkie Pie gasped, loudly.

"I know what the best medicine is!" she exclaimed.

And the world stops.

I know what the best medicine is!

Everything fades away except Pinkie Pie.

I know what the best medicine is.

Pinkie Pie smiles at her.

I only want what's best for you.

She is growing larger.

I know the best medicine.

Twice Rainbow's height.

You can trust me.

Pinkie is standing in a doorway, and she is looking down at Rainbow.

Trust.

Two wings are growing from her back.

Me.

Pinkie gives them a flap, then folds them on her back.

I'll help.

The rest of the room is appearing.

I know best.

Bright-yellow walls, with Wonderbolt posters.

This is for the best.

This is Rainbow's room, in Cloudsdale.

This will make it better.

Pinkie is changing colour.

This is what's best for you.

She's blue now.

This will make you understand.

Her hair is changing, too.

Will make you learn.

Less frizzy.

To be nice.

Wind-swept.

To behave.

Rainbow-coloured.

To be careful.

Pinkie's features grows thicker, more angular.

To think ahead.

She's a stallion.

To do what you're told.

There is a broken vase at Rainbow's hooves.

You won't repeat those silly mistakes.

Pinkie's smile turns into a frown, and her eyes a hard yellow.

I'll make sure of it.

Her father steps into her room. He closes the door behind himself, and walks to her.

Rainbow tries to back away, but she can't move. She can't breathe.

"You've been misbehaving, Rainbow." Her father is towering above her. His face is a perfect picture of contempt, and his eyes are boring straight through her.

"I know the best medicine for that."

He swings a hoof. Rainbow screams, but there's no sound. The world collapses and she is falling, faster and faster downward. Her father's hard and cruel laughter drowns out the sound of her pounding heartbeats. A black shadow grabs a crushing hold and pulls her further down. She can't move, can't struggle, can't escape. Her vision floods with darkness, and

"Listen to this one!" Pinkie Pie says, excited.

Rainbow is thrown back into reality, hyperventilating. She is sitting outside, at a café, in Ponyville. Her best friends are all around her.

Pinkie Pie tells a joke, and everypony laughs. Rainbow's is hollow.