Sunset Shimmer was really a giant spider the whole time.
Casting aside her bricks and mortar, she jumped atop the wheelbarrow and began to cackle monstrously. "Ahaha, you fools! I was really a giant spider the whole time! And now that Twilight Sparkle has left and taken her magic with her, I'm free to rampage, kill, devour, and jaywalk!"
Some of the students who were leaving the Fall Formal looked her way. But most did not. Rainbow Dash and her plucky friends, whom you may remember from the spinoff series The Rainbow Dash Show, were among those who did. Rainbow Dash, the unquestioned leader of the gang, authoritatively spoke for them all when she said, "What?"
Sunset's face took on a look of sour milk and sputum. From out of her magical leather jacket, she pulled two new pairs of arms and screwed them in. If you thought she looked cool in that smokin' leather jacket with just one pair of arms, well, imagine that but nine times as cool. (Remember that coolness is proportional to the square of the number of arms.)
Pinkie Pie gave a loud gigglesnort. "Wow, I didn't know we were in the middle of an arms race!"
Applejack chimed in next. "Sunset, I would have thought you'd learned your lesson by now. Don't you know that starting an armed rebellion is treasonous, and that treason is punishable by execution?"
Rarity blustered. "Makes sense... that is an Armani jacket, after all."
"Shut up, Rarity."
It doesn't matter who said that last bit. They were all thinking it.
"That's enough out of all of you... you!" Sunset gestured vaguely with two of her arms in the general direction of the Rainbow Dash Gang. "I'm transforming now, and afterwards I'm going to gobble this town all up! Yum yum! Don't even think of trying to interrupt me during my glorious metamorphosis!"
Rainbow Dash checked the status of her party members. No injuries except her own cracked tailbone, which was an insubstantial penalty to dexterity, especially considering her build. A snarl-grin snaked across her face. "Are you ladies thinking what I'm thinking?"
Applejack flexed her manly biceps. "I'm on it, Dash. I'll give 'er the Sweet Apple Acres Haymaker!"
"No, no, Applejack, not that. I was thinking of something a little more... awesome."
Pinkie Pie's eyes, I shit you not, they got even bigger than they already were. "No!"
Fluttershy quietly gasped. "You don't mean...!"
Rarity blustered. "Oh, we simply couldn't!"
"Ohhhh yeaaaaah!" Rainbow Dash's hair turned all attack-mode red, and her cheeks glowed with the red-hot fire of discarded childhood dreams. "Formation, girls! It's time for us to finally use... pause for dramatic effect..."
The silence was not so dramatic as all that. Some drunk high school girl was getting it good in a parked car nearby, and she was making a decent little fuss about it.
"...the Dash Attack!"
Fluttershy sneezed. "But Rainbow, we've never done that attack before! I know you've been waiting for years for a chance to perform that attack in a no pretending, for-realsies fight, but I don't think we're ready!"
Rainbow Dash let out a war cry. "Take heart, my yellow-bellied comrade! The Dash Attack can interrupt anything at all! And since this is a crisis, we'll no doubt be pushed beyond the limits of our normal abilities, and discover the hidden strength that's been inside us this whole time!"
As she said this, a bone-splitting crackling sound grabbed her attention. She looked back over her shoulder, and saw that Sunset's mega-evolution was already accomplished.
Rainbow gaped for a moment while the realization sunk in, and then let out a sigh as her face and shoulders fell.
"Maybe someday..."
A giant ketchup-and-mustard spider was towering over them. It was the legendary Sunset Spider. Everyone has heard the legends.
As foretold, Sunset Spider's first act was murder. She dropped her oversized abdomen down plop on top of Snips's torso, and he burst like a pimple; Snails she rolled out and twisted up like pretzel dough.
Applejack elbowed Rainbow in the ribs, muttering, "Gee... I knew Sunset was into the Noble Eightfold Path and all, but this is ridiculous."
Sunset's eight bright red eyes wonderfully complimented her eight knobby legs and her fearsome, snapping, poison-tipped chelicerae. "Ahaha! Who's the awesome one now, Rainbow Ass? Now to implement the next part of my evil plan, and drape the city in my patented red and yellow silk!"
Rarity blustered, "That sounds... quite agreeable, actually."
"Shut up, Rarity!" Sunset Spider grew angrier. In a great heave of disdain, she lumped a swatch of silk skyward, which exploded in midair like a feather pillow. The silk fluttered downward, and carpeted the neighborhood in a horrible sticky skankflood that was, per unit weight, stronger than steel.
Pinkie couldn't help herself. "Oh no, guys, it looks like we're in a sticky situation!"
Applejack followed suit, trying in vain to wriggle free from the slut sauce confining her. "I can't believe it, Sunset. All this time we thought you were a human, and then a pony, but you were just spinning a giant web of lies!"
Rarity blustered, "This is an arachno-tastrophe!"
Everybody winced.
Sunset advanced upon them. "I'm going to dissolve you all in an acid bath, and drink you like a Slurpee! Now that I'm a giant spider, I can eat what I want, when I want, and never have to worry about gaining weight! Hee hee! No more bathroom barf trips for this bitch! Calories, calories, calories! Ahahahaha!"
Rarity died first. She looked even more fabulous as a sack o' bones.
Fluttershy went next. Her final words were, "I always hoped I'd be killed by an anim—GLUGURRHH kekkk kukkkk oiyghh pttt pttooo."
Applejack and Rainbow Dash went out fighting, like all men should. It was a good death and it made their families proud. They died in each other's arms that day: a fitting end for such close brothers-in-arms.
As for Pinkie, everyone at school loved her, and we all knew she lived her life to the fullest. More fully than any of us were brave enough to, anyway. I guess that's why she was voted Most Likely To Succeed. And, too, I guess it's no surprise that she ended up dying young. That's what happens when you burn the candle at both ends, the way she did. I've lived a long time since then, and seen a lot, but I still to this day think about Pinkie from time to time. I'm sorry to admit it, but I never did find out what became of that gal. After she died, I mean. Her last words, recorded in the yearbook, were: "Her giant chelicerae are ripping my guts out! Haha, get it? Chelicerae? Wait, that's not funny..." *gurgle* *cough*
As for me: a few weeks after all this happened, Sunset called me up and asked if we could get back together. I was in a forgiving mood, so I agreed to a dinner date. Long story short, we've been married now for almost fifty years. And I'll never forget the evening we first rode off into the sunset together—me with my guitar, her with her gastric juices and ten-story appendages.
God, I love that girl.