"I don't know, Twilight," came the soft and reserved voice of a young dragon from the corner of the room, his clawed feet hot with sweat against the wooden library floor. "This spell seems way above your pay grade, if you know what I mean."

"Nonsense, Spike," the living embodiment of pony science dismissed, trotting around her table and examining the spread of scrolls, books, potions and runes that covered it with extreme focus. "If the princess was worried that I couldn't handle it, she would have said something in her letter when I broached to her my desire to experiment with hormone-altering magic."

"Yeah, right. Sometimes I think Celestia just likes to mess with ponies and not tell them things, so that they learn things for themselves the hard way." Spike muttered under his breath.

"What was that, Spike?" Twilight asked absently, igniting her horn and levitating a few liquid-filled test tubes around in front of her face. Deep in concentration, lost to everything outside the realm of magic and science, Twilight's mind had no room for dragon sarcasm. Spike shrugged and shook his head. His surrogate unicorn mother could be so dense.

"Remind me again what it is you're actually trying to do?" The dragon inquired, walking over to the base of the library's staircase and sitting on the lowest step. Clasping his chin in his claws, his eyes glazed over in watching numerous objects float about the table, suspended in Twilight's magical aurora. From what he could tell she was examining one of her giant dusty books, flopped down in the center of the table.

"Hmmm...well, right now I'm trying to calculate the amount of milliliters I'll require from each separate potion ingredient. Any incorrect amounts, and the spell won't work," she explained, "but, as I told you earlier, the ultimate goal is to create a potion-based spell that will successfully stimulate and control certain aspects of a pony's hormones."

"And...this is important, why?" Spike inquired further.

"Hormones are like messengers of the body, Spike. They tell the cells of the body to do certain things. They're a fundamental part of the body's network of communication and function, as well as growth. By being able to control them, all sorts of spells for altering the strength in muscles, energy input and output and other things could be easily developed."

The birds were chirping outside. Two birds, Spike noticed. One male bird was chasing the other, a female, around one of the tree houses' branches. While the female had been on the branch for quite a while, she was soon forced into the air by the male, who had decided to give chase. Huh. Maybe they were playing, Spike thought. Birds probably got bored and liked to have fun too, right? He knew Peewee did. And, well, he was kinda sorta a bird, too.

"Aaaand...done! Haha! Spike, I think I did it!"

Spike's complete lack of focus at last dawning on him, he cleared his head from his thoughts and glanced back to the table. While Twilight merrily bounced in place somewhat reminiscent of Pinkie Pie, the previously floating test tubes had been laid back in their coasters, empty and drained of their contents - contents which now mixed and fizzed ominously in a central jar, just in front of that huge book.

"Uhhh...Twilight? Is it supposed to be doing that?" Spike asked wearily, instinctively getting to his feet, butterflies filling his belly. Oh, man. That fight or flight moment was coming to him. Rather in this case, a 'tackle Twilight out of the way' or flight.

"It's only settling, Spike. Once the chemicals stabilize it'll be fine." Twilight reassured, ceasing her bouncing and moving the jar aside carefully while she looked back over the book. But despite her words, the jar's hissing grew in audibility, and the base of the jar tinged with a sudden fit of shaking.

"Twilight, it's not settling, it's not settling!" Spike exclaimed, grimacing and throwing his hands over his head in tense anticipation for a bang, or other form of unpleasant explosion. Only now did Twilight turn her full attention to the jar, and begin to understand a bit of what Spike was feeling. That was anything but a stabilizing potion.

"Uh oh...I think you might be right!" She whimpered, ears flattening and lifting a front hoof in anxiety.

Horn igniting once again, the purple unicorn grabbed the jar and lifted it high into the air, before securing it in a spherical shield of magical energy. There, it continued to shake uncontrollably, droplets of light blue potion spilling over onto the lower portion of the shield and fizzing into an opaque smoke. As seconds went by, the dissipating droplets grew into a thicker smoke, and both Twilight and Spike felt their heart's skip a beat...as the smoke filtered through the force field.

"W-Whoa! Since when can smoke do that!?" Spike shouted, ducking for cover under his blankets.

"I-It's magically imbued, Spike! The ingredients making it up have magical energy inside them, my magic can't contain it! Oh no...I-I need to get this out into an empty open space! It needs to dissipate naturally!"

With that, the frantic unicorn used what focus she had left in her horn to slam open her front door, and run outside with the seething potion a few feet in front of her. Spike crawled out from his bed and bit his lip, swallowing hard. Should he follow her? Would he just get in the way? Oh man.

"Come on Spike, Twilight might need you! Number One Assistant, remember?" He whispered to himself, jumping up with heroic tenacity. Grabbing a spare piece of parchment for a letter to the princess, the young dragon ran from the tree house after his frantic friend.

--

Oh no oh no oh no oh no oh no oh no oh no!

Barely observing the ground in front of her, Twilight tore through town, the blue potion and its vastly thickening smoke flooding out of her force field steadily. A few passerby ponies gasped and leaped out of the way before they got bowled over, while others stared on in confusion at what their crazy librarian resident had done this time.

As she crossed the bridge connecting town to the fields and hills that lead to Fluttershy's home and, eventually, the Everfree Forest, Twilight bit down on her lip. Just a little further, and she'd be set. The smoke would be able to spread out into the open air, and break down into completely harmless particles. But, what had she gotten wrong? Why was this happening? She couldn't have gotten the potion, or any of the enchantment spells wrong...

"Twilight!" came Spike's voice from several hundred yards behind. The dragon was panting, standing on the bridge and clutching his knees.

"Spike, I can't! Not now!" She yelled, keeping her eyes on the potion and the approaching field in front of her.

"But Twilight! Watch where you're going! Twilight!"

"...?!"

Too little, too late. In a single moment, Twilight felt a sharp pain shoot through her front left hoof as it collided into a lowly-embedded rock, hidden in the thick grass. A wince and gasp was followed by a thud, a yell, and a splash. Spike gasped, covered his mouth for a moment in shock, then ran towards the cloud of smoke.

"Twilight! Oh man. Are you okay!?" Spike shouted, covering the distance in no time and getting to a close, but safe distance from the fallen mare, who was still engulfed in the slowly fading smoke. While having caught the glass jar with her magic before it fell and shattered, her force field had broken in the sudden loss of focus from her fall, and the potion, oh the potion...had poured right out.

Slowly but surely, the smoke dissipated as oxygen dispersed it. Spike began to take notice of his friend's silhouette moving, and he sighed a little in relief.

"Didn't I tell you to look where you were going?" He scolded, cocking an eyebrow and crossing his arms. "You always freak out like that, then end up flopping over yourself. Heh, good thing you got your Number One Assistant here to keep...you...whoa."

"*cough* *cough*! S-Spike, what are you-...*GASP*! Wait, what the hay happened to my voice!?"

The smoke had finally faded almost completely, and the purple unicorn stood up straight, hardly the same unicorn that had fallen. Spike, still speechless, gawked slightly at the firmer, bulkier build, the lack of eyelashes, the larger chin and, perhaps most noticeably, the choppy, short mane style. As Twilight began to look around at her new-found body, whimpering and losing her stability more and more every second, Spike got up as well and put a hand on his chin.

"Dude...you're a guy."

"Ohnoohnoohnoohnoohnoohno!" Twilight panicked, fluttering in place on four hooves nervously as if the ground were on fire, and looking around with wide, scared eyes to see if anypony was there to see. Spike had to admit, it was a whole lot funnier coming from a stallion - he actually had to stifle a laugh.

"This can't be happening! There's-there's no way!"

"Sure there is." Spike said calmly. "It's called, 'Spike was right all along, and dealing with all this hormone stuff is definitely way above your pay grade.'"

Twilight craned his neck and shot the dragon a quick glare, before returning to panicking outright.

"N-no, this is serious, Spike. We need to fix this right away. There might be other horrible side effects as well, or..." The stallion stopped mid-stride. "...or it might even be permanent! Spike, what will my friends think? What if this puts an awkward dent in our relationship!? What if they don't want to be friends anymore!?"

He trotted around nervously, practically pacing in a wide circle around Spike, who couldn't be any less bothered, as if he was already used to Guylight Sparkle.

"What's EVERYONE going to think? I-I've never been a stallion before, I-I don't know how to be one!"

"Being a guy is easy," Spike said, laying on the grass and lounging with his claws behind his head. "You just be cool, relax, and let the flow take you where it goes. You'll get used to it no time. Then you can just find a way to turn back. Piece of cake!"

"I don't want to get used to it at all, Spike!" The stallion yelled impatiently, flaring up his horn and floating the young dragon onto his back. Spike landed with an 'oof', muttering about how less soft it was sitting there, now with Twilight no longer being small and petite. After a few moments of horn charging, the two vanished in a flash of bright light, reemerging back at the library a few seconds later; still quiet and peaceful, albeit a tad messy.

Jumping off from his new guy friend, Spike stretched and laid down on his bed, watching the purple stallion fuss around with the scrolls and books that still lay open on the desk.

"So, what are we gonna call you now?" Spike asked aloud, watching Twilight frantically search. "Guylight Sparkle? Maybe Twiguy? Huh...what's like 'Twilight' and 'Sparkle', anyway?"

"Spike, this isn't funny." The lower-toned stallion snipped, flipping through pages of several books all at once, trying to find anything he could regarding gender changing. But from cover to back, not a single solution could be found. Everything from muscle alterations to energy fluctuating danced around the pages in great detail, but the most unimaginative and outright change of all was nowhere to be located. Twilight's heart pounded against his chest.

"Oh! I know...what about...Dusk Shine! That's like, the opposite of Twilight, and something other than Sparkle!"

"SPIKE, KNOCK IT OFF ALREADY!" Twilight growled, giving him another glare. "Can't you see how serious this is!? I can't find a bucking thing about gender changing in any of these books, and those ingredients from earlier where most of what I had! What if I'm stuck like this forever!? What if my friendships fall apart and I lose all contact with Ponyville and all its' ponies!? What if I-...what are you doing?"

Halfway through 'Dusk Shine's' rant, Spike had rolled his eyes and gotten up from his comfortable napping position. Taking out the scroll he had been hanging on to since he left, he pulled out a spare quill and a bottle of black ink, and had begun to write. By the time the ranting unicorn had taken notice, the dragon had finished his short message, wrapped it up, and flashed it away in a flare of green fire. Dusk looked on in horror, mouth agape, while Spike cocked his eyebrow in retort.

"Well ya know, it just occurred to me, if you're gonna be all grumpy now that you're a guy, maybe it is better if we turn ya back as soon as possible." The dragon said with deadpan. "So...how about we stop freaking out, and wait to see what the princess has to say, huh? I'm sure she can fix you."

"Spike! What did you do!?" Dusk fretted, running over to poke his head out the window, trying to catch glimpse of the traveling fire mail. "The last thing I need on top of this is for the princess to see that I messed up so bad! UUUUGHHHHH!"

"Oh, calm down. I just told her that you needed some help with a mistake you had with the hormone spell, and that you don't have the stuff to fix it. Do you seriously never remember all the times you've totally flipped, and then come to realize you were just overreacting? Like that time where you couldn't get the princess a letter on time, and went completely wacko?"

Twilight 'Dusk Shine' Sparkle sighed to himself and teleported up to his bed with a spark, worry about his new appearance and confusion about what he had gotten wrong swimming around in his head like a pack of piranha. Flopping down on his bed, he buried his snout into his pillow, flank sticking up in the air amusingly as he groaned a young teenage boy groan.

"...Mwhat mam mai rowing ro roo...?"

"Didn't quite catch that one." Spike said.

"What am I going to do!?" Dusk repeated, roughly grabbing his blanket with his magic and throwing it over himself. Spike bemused the fact that the stallion's rump caused the blanket to stick out. But just as Spike opened his mouth for another witty comment, he felt something warm rising up his body briskly. His gag reflex activated within seconds, and with a loud, unyielding belch, a flare of green flames shot forth, dropping a fresh scroll onto the floor.

"That sure was fast." Spike said, punching the scales on his chest to let loose a smaller excess of flames before picking up the scroll. Unraveling, he looked it over and began to smile.

"Well, what's it say?..." Dusk asked timidly, horn and snout poking out from under his blanket, anxious anticipation gripping him, as usual. "Am I stuck as a boy, forever? Is there no cure? Is she mad at me? Am I going back to Magic Kindergarten...as a boy!?"

"'My most faithful student, and trusted assistant, Spike," Spike began to read aloud, putting proud emphasis on the second line. "'There is nothing wrong in making mistakes, as failure only demonstrates that you are truly trying your best. While I am more than happy to assist you in any way I can, I'm afraid I am rather caught up in a series of political situations at the moment. As such, if you require my assistance, you'll have to come visit me in Canterlot, and patiently await a time later today, or even tomorrow morning, after I have settled these current affairs. Only then can I assist you.

Should you need to stay the night, you're more than welcome to stay in the castle; alternatively, I'm sure your brother, Shining Armor, would be more than happy to house you for the night.

Sincerely,
Princess Celestia"

"C-Canterlot? Ooooh, of all the times that her political adviser ponies have to take up all her time, it has to be now!?" Dusk said, twisting around on his bed and staring up at the ceiling, intertwined with his blanket. "I can't go to Canterlot, it'd be an even worse disaster than Ponyville! A-And I certainly can't see my brother! What would he think? I don't want to creep him out! He's always had a little sister, not a little brother! It'd be super awkward...he might even avoid me!"

"Oh for Celestia's sake," Spike said in exasperation, putting down the letter, walking up the second floor steps, gripping the purple unicorn's blanket covers and yanking them out from under him. While Dusk glared and covered his face with a hoof, Spike grabbed his friends' tail and began to pull.

"It's not a big deal, Twilight," he said, straining himself against the noticeably heavy stallion. "No one is going to care, and then once you're fixed, you can look back and laugh about it. The princess has been around for a long time, I'm sure she can fix you somehow."

Dusk didn't budge. Spike rolled his eyes. Time for a new approach.

"Please? Do it for me? You could wear a cloak or disguise or something if you really wanted." He tried, in a much softer, pleading voice. The dragon jumped up onto the bed and gently pushing against the stallion's back.

"...A disguise. Well...I suppose something big enough with a hood would work." Dusk said quietly, thinking over the idea and sighing again. "Alright, Spike. I'll go see the princess. But I'm not going to stay with my brother, and I'm going straight to the castle so nopony sees me."

"Great!" Spike said with glee, throwing his arms around the colt's neck in a hug, and running off to find the largest raincoat he could find.

"And Spike," Dusk continued, getting up from the bed and slowly making his way downstairs. "I want you to put a sign on the library door saying that I'm...uhh...very ill, so the library is closed for a day or two."

Wait. But what about her friends? They'd want to come in and take care of her, if that were the case. Especially Fluttershy...

"Wait, no, that won't work. Put a sign on the door saying that I've gone to...a...mandatory...two-day seminar on magic and friendship." Dusk threw together, getting a questioning glance from Spike, who had found the coat he was looking for. "A seminar that...all of Celestia's students have to go to."

"...Seriously?"

"Just do it, Spike. Now give me that coat."