It's more of a mini-freakout, really
Scootaloo dragged her hoof in the dirt and skidded to an abrupt stop, sending dust clouds swirling through the air. Her mouth moved wordlessly and her face crinkled in confusion as she tried to make sense of what she was seeing. She raised a hoof and pointed; but before she could say a word, she was tackled into a nearby bush, knocking her helmet clean off.
Scootaloo sat up, spitting out leaves and twigs and strands of pink mane- pink mane? She looked over and saw Pinkie Pie, pressing a hoof over her lips.
“Pin-?”
“Shh!” Pinkie shushed her.
“But-”
“Shhh!” Pinkie repeated, a bit more urgently.
“I don't-”
“Shhhhh!”
“Shh yourself!” Scootaloo hissed back, shoving Pinkie’s hoof away. “What's going on? And why does Rarity's mane-”
Pinkie quickly clapped four hooves over Scootaloo's mouth, but it was too late; the damage had been done. A light glow surrounded the filly, and she found herself lifted up out of the bush and plopped down in front of a very disturbed Rarity.
For Scootaloo's part, she was somewhat disturbed, too. Rarity's eyes were wide, her makeup was smeared, and her smile far too wide and tight to be genuine. And then there was her mane…
“What's that about my mane, dearie?” she asked in a voice far too sweet for the situation.
“Uh… it's… great?” Scootaloo tried. “The, uh… brown goes well with your… uh… cutie mark?”
Rarity leaned in close and scowled, sending Scootaloo shuffling backwards. She prodded her chest with the tip of a hoof. “You're a filthy little liar,” she accused quietly.
A yellow hoof rested on Rarity's shoulder, gently pulling her back. “Now, now, Rarity,” Fluttershy soothed her. “She said she liked it.”
“My Diamond blues and and this shade of brown clash, darling!” Rarity spat. “She was just being polite!”
It wasn't often Scootaloo had to deal with this level of crazy. She raised a hoof. “I can be rude if you want?” she offered.
Pinkie's hoof emerged from the bush and quickly wrapped around Scootaloo's mouth, but Rarity lit her horn and pulled it off. “Yes, yes; be honest with me! Tell me how hideous I am! Tell me!”
Scootaloo took another small step backwards. “I was actually going to say your mane kindof looks like the time we tried for our bird watching cutie marks and wanted to watch some eggs hatch.”
Fluttershy brightened. “Oh, that sounds lovely. Did you enjoy that?” she asked.
Scootaloo shrugged. “Apple Bloom stepped on the eggs.”
Fluttershy gasped and her hooves flew over to cover her mouth.
“They were empty,” Scootaloo said quickly. “We kindof misjudged the day; they'd already hatched, like, a week before we got there.” She kicked a nearby rock and scowled. “Also Apple Bloom isn't allowed to use the farmer's almanac anymore.”
Rarity was still reeling. “A… bird's nest?” she squeaked.
Scootaloo nodded. “Yeah; like with the tall, thick grass and the crushed eggshells and the bird poo and…” Her voice trailed off as she realized that she was digging herself into a deeper hole. She quickly reached over and pulled her scooter closer, and she felt around for her helmet. “I mean… I gotta go. I heard Diamond Tiara bragging about the prank she was pulling on Sweetie Belle and I need to go warn her.”
She turned to leave, but Rarity stepped on Scootaloo's tail, holding her back. “Might the prank in question involve something like, oh, I don't know, something as silly as switching my mane and tail conditioner with colored dye?!”
Scootaloo tilted her head to see, and sure enough, Rarity's tail was also thick and green and unruly. She had to stuff her hoof into her mouth to hide her laughter.
Rarity, though, seemed not to notice. She had sat down on the dusty ground and had begun to think aloud. “Oh, no, this simply won’t do. Now that I know the party responsible, I know exactly what I'll do. Oh, I know just what I'll do…”
“Oh my,” Fluttershy said quietly.
“You're not going to do something crazy like track them down and give them goofy manecuts, right?”
“Why, yes; that would only be fitting.” Rarity blinked. “Pinkie Pie, why are you still in the bush?”
“I think the real question here is, why aren't you in the bush?” Pinkie retorted.
Rarity blinked flatly. “Oh, I don't know… might it have something to do with the fact that I don't want sticks and leaves and other extraneous items in my mane?”
Pinkie considered this, and stepped out of the bush with her nose held high--and a smattering of branches sticking wildly out of her mane and tail. “Point well taken,” she said.
Rarity nodded, rather satisfied with herself.
Fluttershy spoke up. “I'm not so sure that's such a good idea,” she said. “I'm sure they're very sorry.”
“Oh, they will be,” Rarity seethed. “I will personally make sure of that!”
But before she could expound on that, a bird flew down and landed in her mane. He chirped happily as he scratched her head and turned around, clearly claiming this wonderful nest as his own.
Fluttershy gasped. “Mr. Bluebird!” she scolded. “You get out of Rarity's mane right now! You know better than to use ponies' manes as nesting material!”
Rarity’s face fell, and she slowly sank to her haunches. She whimpered, and her eyes welled up with tears.
“Oh, come on, Rarity. It’s not that bad!” Pinkie said brightly.
Rarity swallowed and blinked the tears away. She straightened up, making Mr. Bluebird fly away in surprise. “I suppose you're right. I can’t be sitting here feeling sorry for myself; there's simply too much to be done." She stood up. "Well, I'm off to the spa, where I shall remain until my mane is back to its normal, beautiful self; and then I shall sit in the mud bath and plot my revenge for hours upon end.” She waved a hoof cheerily. “Ta-ta!”
The other three ponies watched as Rarity pranced off.
Fluttershy whimpered. “Oh, I hope she doesn't do anything too drastic,” she murmured.
Scootaloo quickly jammed her helmet back onto her head and hopped back onto her scooter. She buzzed her wings in preparation, as if warming them up.
“Where are you going?” Pinkie Pie asked.
“To find Sweetie Belle and Apple Bloom. They're going to want to see this!”
Author's Note
I don't know what Rarity's revenge would include. Probably something only she would find horrifying, like informing them that their new top-of-the-line dresses are actually last season's designs.