"Uh, this doesn't really fit me, Twilight," Rainbow said, struggling to tighten the armor around herself so that it wasn't hanging limply off to one side or another.

Twilight Sparkle waved a dismissive hoof. "It's fine, just make sure it's on you. How well it fits you won't be an issue after we start."

"So what's the deal with all this? Why me?" Rainbow asked, finally managing to balance the bodypiece on her wing joints and slipping her hooves into the hoofguards. Her tail had been tucked through the rear end of the platemail lying across her back, their rainbow colors completely hidden within blue decorative fringe.

"Well," Twilight said in a tone that immediately alerted Rainbow Dash to Twilight's 'lecture mode,' "when Starlight sent me through time, one of the possible futures I'd seen was one where Sombra had returned, re-enslaved the crystal ponies, and forced them to fight in a war against Equestria."

"And?"

Twilight shook her head. "The Imperial soldiers wore helmets that, from what I'd heard, made them surprisingly strong and skilled in battle. That kind of resource would be invaluable for Equestria. Can you imagine if you could just put on a set of armor and you'd automatically learn all you needed to know about being a guard? And that could expand to other occupations too. Just think, you could become an expert in something with a mere change of clothes! It would revolutionize entire industries!"

"Uh huh. And how does that affect me?"

"This is just a test run to see if I can tweak the normal EUP body armor enchantments. If it all works, then I can move to more extensive spellwork."

"I don't know Twilight," Rainbow mumbled as she shuffled around in hoofguards a couple sizes too loose for her. "Sounds like you're playing with a lot of unsafe stuff."

Twilight hesitated. "I know, it sounds dangerous, but as long as the use is benign, it should work out, right?"

Rainbow didn't know what "benign" meant, but she hadn't remained Twilight's friend this long without trusting her at least a couple times. "Whatever you say, Twilight. Just promise me if something goes wrong you'll fix it, okay?"

Twilight nodded. "You know I could never forgive myself if I didn't. Ready for the pièce de résistance?"

"As I'll ever be," Rainbow said as Twilight levitated the helmet piece over top of Rainbow Dash's head, sliding it over Rainbow Dash's ears and on top of her mane.

"Now, the first thing that'll happen is your body will fill out to fit the armor pieces," Twilight said as a chill ran through Rainbow Dash's body. "This isn't any new magic; the Royal Guard enchants all its armor this way."

"So I'll- eep!" Rainbow interrupted herself as she felt her hooves begin to swell. Resisting the urge to jump, Rainbow looked down and saw her muscles began to grow and ripple with new power. "This feels really weird, Twilight!"

Twilight nodded. "Don't worry Rainbow Dash, this is normal. I promise, if anything unusual goes on, I'll reverse the enchantment immediately."

"Still feels weird." Her leg muscles grew larger and denser, spreading at a rapid pace. Rainbow Dash shuffled her hooves, only to realize that the golden cups they were in fit perfectly. "Hey, these things fit now."

"What did I tell you?" Twilight smiled, flicking her eyes occasionally to a paper full of scribbles she had on a nearby table. "I wouldn't have even had a place to start if EUP armor hadn't been made like this. It's really been a huge help in my research."

Rainbow Dash did her best to concentrate on Twilight's words, but her stomach was doing flip-flops inside her as her torso barrelled out and gained muscle mass. She felt a twinge between her hindlegs, and such an enormous wave of embarrassment came over her that she shoved out of her mind the idea of even thinking about her new plumbing. Her wings twitched involuntarily, beefing up to handle Rainbow's new weight; the pegasus spread them, trying to get them to relax, only to realize she couldn't close them again. "Twilight, I can't close my wings!"

Twilight looked up, an expression of slight concern on her face. "Well, give them time to finish, then see. I didn't tamper with any of the magic in this stage except to remove the fur bleaching to white, so it's very unlikely for there to be problems."

Despite Twilight's reassurance, Rainbow's unease didn't fade as her wingspan lengthened by several inches and new feathers grew out to join those already there. Despite finally being able to pull her wings back to her sides, her body felt misshapen and wrong. "Twilight-"

"I know," Twilight interrupted. "It probably feels like you're in the wrong body, but don't worry, once the changes are done, that'll be fixed. Like I said, the parts of armor enchantments like that are how I managed to figure out a way to implement my idea in the first place."

Rainbow whimpered as her pectoral muscles bulged to fill the chestpiece perfectly. "It better finish soon."

"It's only been about a minute, Rainbow. It'll be over before you know it."

Rainbow stood, barely fending off the urge to whine through her nostrils as her neck thickened and lengthened. She realized that with her gains in height from her hooves and neck, she now stood about a half-head taller than Twilight. The only patch of fur that she could see on herself that hadn't changed shape was the small amount of blue on her muzzle in front of her vision, and she knew that with her neck altered, it was only a matter of time before her face changed too.

"Twilight, I-" Rainbow Dash's hoof jerked up to her mouth, the metal of her hoofguard smacking against her lips harder than she'd intended it to. However, the mild sting of hitting herself was dwarfed by the shock of her voice sounding deeper and huskier. "What happened to my voice?"

"That's normal too," Twilight said. "It's actually rather interesting; vocal chords have a special sub-enchantment to them to tweak them to suit the armor, but unlike everything else, there's no 'template' for it to work off. It actually modifies the vocal chords itself. I would guess it's probably to ensure that all guards don't sound alike."

Rainbow Dash quit paying attention, feeling the magic tingling in her mouth. The small patch of blue fur still visible in front of her began stretching forward, and she screwed her eyes shut, willing herself not to panic as she felt her jaw and muzzle shift into more chiseled features. Her eyes itched, and she reached up to rub at them with a hoof, careful not to hit herself with her hoof plating this time. She felt something flake off, and she opened her eyes to see several eyelashes on the cup of the hoofguard.

Something smooth and airy caressed her head, and she felt her mane grow and twist underneath her helmet.

Twilight nodded. "Okay, I think that should be it for physical changes. Now begins the mental parts."

A slight pressure built behind Rainbow's eyes, and she clenched them shut again, flinching away. It wasn't painful, but it was definitely unpleasant.

"Oh, here," Twilight said suddenly, telekinetically pulling a full-size mirror in front of Rainbow. "If you want it."

Rainbow Dash looked in the mirror; a well-built stallion looked back. Muscular frame, large wings, angular jaw, sharp eyebrows. With her cutie mark covered by the armor, she could have passed for an actual guard in the Royal Army if she dyed her coat white.

As Rainbow Dash took stock of herself, she realized she was feeling more at ease with her body. Her brawny girth felt natural to her now, and as she thought about it further, she could almost detect a foreign force inside of her working away to ease her dysphoria. The feeling faded, and Rainbow Dash realized that she felt as if she'd always had the body she now possessed.

"Wow," Rainbow Dash said. "This is surreal." Even her voice sounded right to her; despite knowing, without a shadow of a doubt, she'd only possessed her gravelly baritone for the last couple of minutes, it was undoubtedly hers, and hearing anything else would have sounded strange. "Everything just feels... normal." She flexed her wings, admiring how natural it all felt.

"Anything else?" Twilight asked. "Perhaps... anything about your identity?"

"Identity?" Rainbow Dash searched inside herself, trying to feel out where the magic twinge was like she had when it had made her feel comfortable in her new skin. She found... wait, there. She. Wasn't she a she? She stood there, unsure of how to feel as she realized that "she" might not be the best pronoun for her any more. Again, she knew that she had spent her entire life as a mare up until she had donned the armor, but now... now he just didn't feel like he identified as female any longer. It just... wasn't him. And his... parts. He wracked his brain, trying in vain to remember how his old equipment had felt, but he couldn't begin to grasp how it might feel. He was a stallion, inside and out.

"Yeah, I guess I'm a guy now," Rainbow Dash said, his head spinning with confusion. "I'm... what in the world is in this helmet? I should be ticked off at this, but it's like getting annoyed at having a nose. I should feel angry, but I don't."

Twilight lowered her head, a sheepish smile stretching across her face. "Sorry, that's how all the armor works. Celestia decided centuries ago that it would be easier for enlistment purposes if she could admit, er, scrawnier ponies, so she and a bunch of other unicorns drafted up a spell to give anypony who donned the enchanted armor the physique they needed to fight. It was so successful both in peacetime and in battle that it's been that way ever since. My only addition so far has been the gender identity enchantment; normally there are only adjustments to make sure ponies feel like they're in their own skin." Twilight's smile wavered. "Normally they have both male and female armor, but I felt that going across genders would make for a more measurable change."

"So is that it, then?" Rainbow asked, still trying to deal with the shock of knowing that his physical form had completely changed, yet he felt like nothing was different. I wonder if I could pull off a Sonic Rainboom in this body right now.

"Not quite," Twilight answered. "Give it a minute."

The pressure behind his eyes returned, but Rainbow didn't flinch away this time, trying his best to bear it. His mouth twitched into a smile; with how comfortable he felt now in his body, he could probably mimic the Guards' disposition if he applied the discipline of Wonderbolt Academy to himself at this point.

The magic poking around in his head felt much less refined than the near-flawlessly smooth movement of the armor's original enchantments, but he could tell that it was still quite graceful as it flitted here and there in his mindscape.

"Look at me for a second. How does it make you feel?"

Rainbow examined Twilight. After a moment, his eyes widened as he felt butterflies flit around in his stomach. "You... You turned me gay?"

"Well," Twilight said, "Since you're male, it's more that you're technically straight now."

Rainbow Dash blinked, unsure of how to process the information. Of course he liked mares. But... he was a mare not five minutes ago, and he liked stallions then. What? Why did looking at Twilight have to suddenly make him feel so funny?

"You can remove your armor now," Twilight said, looking back at the notes on her table. "Now that the enchantment's complete, you don't need to wear it any more... Rainbow Blitz."

Rainbow blinked. "Blitz?"

"That's your name, isn't it?" Twilight said, her tone carrying a sense of expectation.

Rainbow Blitz opened his mouth to object. Of course his name wasn't Rainbow Blitz! It was... wait... Rainbow looked down, wracking his brain to try to remember what his name was. A numb revelation came over him as he realized that as far back as he could remember, his name had always been Rainbow Blitz. He recalled signing weather duty slips with that name. He remembered the trophy he'd won for the Best Young Flier competition having had "Rainbow Blitz" etched on its inscription. Every single chant he thought back to in his life as he performed for a crowd had been for Rainbow Blitz.

"I... I guess it is." Rainbow Blitz slowly took off his helmet, hoofguards, chestpiece, and platemail, leaving them in a pile on the ground in front of him. His mane and tail had changed, too; his mane had grown even more unruly and spiky, and his tail had taken on a zigzagging pattern.

Twilight's face reddened slightly. "Oh my..."

"What?" Rainbow Blitz asked, doing his best not to think about his name or his new feelings of attraction.

Twilight audibly gulped. "I... I didn't know you'd be so handsome as a stallion."

Rainbow huffed. "Well, what did you expect from the most awesome pony in Ponyville?"

Twilight stepped around Rainbow, examining him. "It looks like this was a success. I removed the pigmentation changes and added the identity and orientation bits, and it seems like it's worked out pretty well. Wow, you look about as strong as Big Macintosh; you could probably give him a run for his money if you two hoof wrestled."

"Yeah," Rainbow Blitz said, flexing his hooves and taking a small amount in pride at how his muscles rippled. "It's really disturbing. I know I wasn't like this this morning, but I can't imagine myself being any different. I did a rainboom as a mare. I grew up as a mare. Now... Now I'm not one."

Twilight nodded. "Do you want to change back?"

"That's the thing." Rainbow swallowed down his growing anxiousness. "It wouldn't be changing me 'back,' because it feels like I've always been this way."

"Well, I didn't intend for you to stay this way. If you want to stay like this, I guess there's no reason you can't, but you'll have to do a lot of explaining to a lot of ponies."

Rainbow Blitz took a deep breath to steady himself. "I... Would that be okay then, if I was just a stallion for a little bit? I didn't know what it was going to feel like before I got into this, and I really didn't like how it felt being in the wrong body, even if it wouldn't last long the second time. I think I need a bit of time before I try that again."

Twilight blinked a couple of times, before nodding and looking back at her notes. "I guess, if you really feel that strongly. But in that case, I'd like a favor in return, if that's alright."

Rainbow's nervousness began stirring within him again. "What kind of favor?"

"I'd like to get regular updates on how you adjust to it," Twilight explained. "Since I assume you'll stay a stallion until you tell me you want to be otherwise, I could use the information to help further my research into this topic. It's a great opportunity for me, and all you'd need to do is come here every so often and answer some questions."

Wow, never noticed how cute she gets when she goes egghead on me. "Sure, Twilight, I can do that."

"Great!" Twilight levitated a piece of paper and a quill from off her table. "I'll go ahead and send some letters to ponies explaining the situation. Celestia, Wonderbolt HQ, your parents, Mayor Mare, our friends, just so that they know ahead of time. It would be pretty awkward if Spitfire called you up and didn't know what happened; the least I can do is make it less weird for everypony."

"Thanks." Rainbow Blitz turned towards the door and began walking. "Speaking of Spitfire, I'm probably going to have to practice my Wonderbolt routines for a bit to make sure I can nail them now, since I've always practiced them as a female." Rainbow shook his head, still trying to get over the fact that he had once been a girl. The idea alone was so alien!

"Good idea." Sounds of quilltip against paper filled the brief pause in the conversation. "I'll just get these letters signed off right away, Rainbow Dash."

Rainbow twisted his neck to nod in Twilight's direction before blinking. "Dash? My name's Blitz, Twilight. As in, Rainbow Blitz?"

A stifled giggle came from the table. "Sorry... Rainbow Blitz."

Rainbow stared at Twilight a second longer before shaking his head, prepping his wings, and rocketing out the front door.

Author's Note

This chapter's premise is partly inspired by ocalhoun's story The Clothes Make the Mare. It's a really good story, I suggest you check it out if you haven't read it yet!