Rainbow Dash liked to show off. This was a known fact, and stating it was like saying gravity pulls things down, unicorns have horns, and Derpy likes muffins. Or Sweetie Belle should be kept away from kitchens. So when she got her belated birthday present to herself and realized how awesome it was, she simply had to let the world know.
Except it was 95 degrees Neighrenheit that day. So she waited.
~Some Indeterminate Amount of Time Later~
Pinkie, Twilight, Fluttershy, and Rarity (Applejack currently had hay fever) sat sipping various beverages in the foyer of the Golden Oaks library, having been gathered here by a rather enigmatic invitation from Rainbow. Who then burst into the tree. Literally, Twilight teleported her in when she saw the pegasus was about to shatter another window.
"Guys! Guys! I know my birthday was When does Pinkie Pride take place? Heck if I know!, but it's been really hot. Now that summer's wrapped up and we finally have some cooler weather scheduled, I can finally show this off! Look!"
At this point, she finally stopped moving around long enough for her friends to take a closer look at the jacket she proudly bore upon her barrel.
It was pretty spiffy. Also pretty brown and leathery. Actually, it was leather. Like, animal skin.
Fluttershy's knees buckled and she promptly fainted.
"Oh my. Dear, is that what I think it is?"
"A super cool jacket? Why yes, it is! I'm glad we can agree on something fashion-related for once, Rarity."
"We all know what a jacket is," Twilight corrected. "We are concerned with what material it seems to be made of."
"Yeah," Pinkie added. "We think you killed a cow to make it. Which you know, can earn you up to ten years in the pen! Fifteen if it's considered a hate crime!"
Rarity and Twilight stared at Pinkie, the later opening her mouth. "Um, I'm a bit hesitant to ask, but... how do you know that specific and mildly discriminatory part of Equestrian legal code, Pinkie?"
"Oh. Long story. Probably one that rhymes with 'Rocks'. It might show up later."
As Fluttershy came to, Rainbow huffed. "Um, hello, guys? This is supposed to be the Rainbow Dash show. I didn't expect Twilight to give Pinkie the Spanish Inquisition!"
"Nopony expects the Spanish Inquisition," Rarity muttered sadly to herself.
"But seriously, you guys,don't you like my cool jacket?"
Twilight sighed a sigh, the same sort of sigh she sighed when Derpy lost her mail or Cerberus left his post or people shipped her with Celestia (Discolight 4eva!) or she was forced to be Sweetie Belle's mentor on a cooking project. A barely suppressed shudder. Never again. Anyway, Twilight sighed, and again opened her mouth. "Did you kill a cow, Rainbow?"
"What? No! Remember that business trip I made to Rainbow Falls? I bought it from the griffin traders there. I just haven't worn it 'cause it's been so hot."
"Okay, so, did the birds you bought it from kill a cow?" Rarity asked. "I wouldn't put it past those ruffians!"
"No, you guys. Geez! You think I'd wear animal skin? This is faux leather."
Fluttershy bravely spoke up. "Rainbow Dash! Foxes are animals too! I'm ashamed of you."
"No, Fluttershy, it's fake! It's faux leather, not fox leather!"
Mares, especially ones who save the world together several times a year, have developed a mystical secret language that baffles stallions, comprised entirely of dubious looks thrown each others' way.
Is this filly serious? Twilight asked Rarity with a wide-eyed glance.
I'm afraid so, Darling, Rarity replied with a tight-lipped nod.
Why are we talking in italics?! Pinkie interjected.
It was Rarity's turn to sigh. "Rainbow. Could you spell out the type of leather your jacket is made of, please?"
"Uh, yeah, I guess. Ef-Aye-You-Ex."
Fluttershy completed the sigh trifecta, but this time the sigh was happy, like her sigh upon learning she didn't have to mentor Sweetie Belle in cooking after all. "Rainbow, that's pronounced '/ˈfoʊ/', not '/fɒks/'."
"Oh. Huh. That's anticlimatic. Next you're going to tell me you don't actually own blind Cervidae."
"Do I? Actually, I have no eye deer."