Twilight walked down the main street of Ponyville with Shadow and Umbra trailing lazily behind. Naturally, because Twilight didn't want the whole town to know about his transformation, they walked under the effects of a fairly powerful 'not my problem' spell and went unnoticed by the townsfolk. It was somewhat concerning how effective the spell seemed to be in Ponyville, almost like the general population had already decided that their royal alicorn was already “not their problem”.

Twilight had chosen Rarity to be the first of his friends to be told as that she usually had the mornings free (Rarity did most of her work in the afternoon and evening) and was considered by Twilight to be one of his saner friends (sane being a very relative term). He was still worried about how his friends would receive his new development, but they are his friends and would never hold something so out of his control against him.

He suddenly found himself standing outside Carousel Boutique. Shadow and Umbra stayed outside as he entered the shop ringing the bell

“Hello and welcome to Carousal Boutique, where every thing is chic, unique and magnif ...” Rarity trailed of as her eyes drifted past the purple stallion that was definitely none of her business.

“There's nopony relevant here”

Rarity walked towards the door, walking around the stallion without consciously noticing him “Must have been the wind or something” Rarity checked the door to make sure it was closed, “Can't be too import ...”

“Rarity”

“... ant” Rarity was suddenly conciously aware of a large, well-built, very attractive stallion standing in the entrance to her boutique, and Rarity felt a headache coming on. “Who ...?” Rarity took stock of the potential customer: horn, wings, purple, strange perception altering magic, male. 4 out of 5 points to ... “Twilight?”

“Yes, Rarity, it's me”

“Spell backfire?”

“Why is that your first guess?”

Rarity gave a deadpan stare.

“Fine, yes.”

“Still working on reversing it?”

Twilight sighed “No.”

Rarity tilted her head in askance.

“It's illegal.”

“Why?” Rarity felt the headache growing.

“Something about it possibly meaning the extinction of ponykind.”

Rarity studied Twilight's face for a few seconds before her eyes widened “You're not kidding.”

“No.”

“Well, then I know what we need.” With a wince Rarity's horn lit up and crystal bottle holding a brown liquid flew into the room, followed by two matching glasses.

“Rarity, isn't it too early for alcohol?”

“Every rule has exceptions, dear, suddenly becoming a stallion and whatever that spell did to me are to exceptions to that rule.”

Twilight's eyes widened, “Oh, psychic whiplash, I'm so sorry Rarity. I guess my physical changes prevented you from subconsciously recognizing me, resulting in the spell effecting you at full power. I guess I probably shouldn't use the SEP field when visiting the rest of the girls then, maybe invisibility.” Twilight shuddered, “I hate invisibility. Did you know I was almost run over by three different carts last time I went out under invisibility, I swear this town ...” Twilight coughed and sputtered as a glass of sherry poured into his open mouth.

“Drink the booze, dear.” Rarity emptied her glass, “And then we can talk about how this all happened.”

Twilight had never known Rarity to use a word like 'booze', maybe the psychic whiplash was worse than I thought he worried as he overpowered Rarity's grasp on the glass in front of him, “It started when ...”

“Tut tut tut, dear. Booze then talk.”

Twilight sighed, then downed the liquor. “It all started three months ago when I visited the Canterlot archives while researching for one of my projects, while there I managed to find a small book knocked over behind the encyclopedia section. It was Starswirl the Bearded's first book of spells, strangely misplaced.

My first instinct was to find the horrible pony who misshelved a spellbook in the encyclopedia section, but I quickly realized that that was unlikely as the book had clearly been there for decades. So instead I decided to skim through it to see if there were any spells that I might be able to cast before returning it to it's proper place.

Most of the spells were, as expected, far beyond my capabilities, but I did manage to find one that looked to be within my own ability to cast ...”

“... and then I walked into your shop, and you know the rest.”

“So, you cast this spell.”

“Yes.”

“And it turned you into a stallion.”

“Yes.”

“And you don't know why.”

“It shouldn't even be possible, it's an purification spell, not a transfiguration spell.”

“And since turning colts into fillies almost caused ponies to go extinct, you can't turn back.”

“It's High Treason.”

“Oh, this is dreadful.”

“It's bucking infuriating.”

Rarity's eyes widened “Twilight! A gentlecolt should never swear in front of a lady!” she scolded

Twilight responded with a glare

“Now, now, don't be like that. You are a prince and a lord, what would the nobility think if they heard you swear?”

“'Hey, it's one of those Twilights, let's continue pretending they don't exist'”

“Exactly, they would be horrifi ... uh what?”

“I'm a Twilight, they're already horrified that I even exist, there is literally no way that swearing could make it worse.”

“I'm sorry, I'm not sure I understand.”

“Of course you don't, now lets talk about literally anything else.” Twilight thought for a moment. “On the subject of literally anything else, you cannot rely on me to use the oestrus suppression spell on you, for obvious reasons”

“That is perfectly reasonable dear. We wouldn't want to have an ... incident, that we would regret”

Twilight grimaced at the thought “Rarity, you did not need to say that”

“Sorry, dear, but it is an entirely reasonable concern”

“I'm not stupid Rarity, I know what heat can do to ponies.”

“I, I would never! I know you are extremely intelligent, but you can be rather naive”

Twilight snorted and started to walk towards the door “Bye Rarity, I have to tell the others.” Twilight grimaced “And I have to start the paperwork required to change my gender on any number of important documents before revealing myself to the general public as a prince”

Rarity's eyes suddenly dilated. “This Is The. Worst. Possible. Thing!” she cried as she faux fainted on a couch that had not been there a second earlier.

Twilight rolled his eyes at her typical melodrama “What is it now Rarity”

“It is an utter travesty that such a handsome, attractive prince, such as yourself, does not have a single dashing suit in which to show yourself off to the mares”

Twilight just stared, unable to formulate his response. Completely ignoring the part about showing himself off to mares. Rarity had just called him handsome and attractive; two things that he had never expected to be called by the fashionista who seemed to have unreasonably high standards when it came to stallions.

“Oh, I-DE-A. I will make you an entire wardrobe that will make you the envy of all stallions and the desire of all mares”

Although he was disturbed by the 'desire of all mares' part Twilight knew better than to refuse a gift from the Element of Generosity “Well you have my measurements, I will be going now” he said as he turned to leave

Twilight felt himself being grabbed by a deceptively strong telekinetic field “Oh no you don't.” Rarity pulled him over to her and looked up at the taller stallion “I fear your measurements may have changed”

Twilight blushed abashedly and chuckled nervously. “But, I need to go. There are so many things to do”

“Come, we must get you properly dressed for your station” Rarity said as she dragged the uncooperative prince into the bowels of her shop “Don't worry I will be quick”

Two hours, forty seven minutes and thirteen seconds later Twilight was standing duty as the model to Rarity's creative whims.

Unfortunately Rarity – while a brilliant dressmaker – had little to no experience making suits (in fact her only experience with a male form was with a young drake with twenty to thirty years to go until puberty) and as such the last two and a half hours were among the most gruelling times in Twilight's life (which is saying something considering Twilight once had to hold an arcane shield for three hours against constant bombardment by eight guardsponies as part of a test). Between a large number of suits that were much too tight in all the wrong areas, a rather full (and terribly delayed) schedule and sheer boredom; Twilight had never been so anxious to leave a place before in his life.

“Twilight stand still”

“Whyyyyy?” Twilight moaned

“Oh, stop it Twilight; you're worse than Rainbow Dash”

“Rarity, we've been at this for almost three hours”

“You can't rush perfection dear. Anyways we would be done already if you did not complain every time you got slightly uncomfortable”

Twilight gritted his teeth “The pain was almost incapacitating, Rarity”

“Twilight, I am doing something nice for you, and all I get is negativity from you. Why don't you be a good stallion and stand there quietly?”

Rarity did have a point; Twilight had been rather negative about the whole ordeal. After all Rarity was making he an entire wardrobe for free, and Rarity hadn't even tried to put gems in the suits (Twilight's aversion to gems was entirely to do with not wanting his subjects to confuse him with a male hooker and absolutely nothing to do with the fact that gems aren't very masculine). Also Rarity's flanks were not bad to look at ... Twilight's mind ground to a halt, derailed by the immensely alien thought.

“See, Twilight, was it that hard to stand still. Although, you don't need to be that stiff”

Rarity walked right past Twilight – tail swaying happily – and levitated two practically identical rolls of dark blue cloth “Which colour should I use for the trim of this suit, Twilight”

While, before, Twilight hadn't noticed his glance fall on Rarity's backside, now it was all too apparent, as he was unable to take his eyes off of the mare's rear. He watched as the well groomed purple tail swayed left and right; enticing him with the possibility of revealing what was hidden beneath, but never revealing more than the slightest glimpse of the mare's most secret place.

“I understand, Twilight. It is so hard to choose. Luna's Canvas gives an air of mystery and subtle power. While Deep Indigo has a strong, powerful presence.”

Twilight – who would normally be wondering if there was any difference between the colour of the two rolls of fabric, other than their names – was much to enthralled by the mare's body to hear the mare's words.

“Oh, I-DE-A!” Rarity trotted over to a rather large chest “I think I have a small amount of it in here somewhere” She leaned into the chest, raising her rump into the air.

Twilight's eyes dilated and his pulse accelerated as he watched the white mare's hindquarters rose into the air; tail no longer capable of maintaining her modesty. Twilight knew it was wrong to look at his friend like this, but he was unable to turn away from the entrancing sight of Rarity's nether parts.

'Rrrrrrriiiiiiiiiiip'

Twilight was shocked out of his leering by the ripping and tearing of fabric.

“Twilight, dear, what was that?”

The answer to Rarity's question came to Twilight in the form of a rubbing sensation against his left rear leg. Mortified was much too weak a word to describe what Twilight felt.

Rarity pulled herself out of the chest levitating a smaller roll of fabric (that was also indistinguishable from the 'Luna's Canvas' and 'Deep Indigo' rolls of fabric) “Twilight, I found the perfect colour for your , it's called Black Amethyst. ”

Twilight, however couldn't care less about fabric at this point in time

Rarity turned around and walked around to the furiously blushing stallion while “Twilight, what is the probl ...” Rarity trailed off as she trotted behind the alicorn stallion “Oh, my”

Twilight's legs gave out and he fell to the ground in shame “I am so sorry Rarity, I was looking at you in bad ways, I just couldn't control myself.” Twilight started to sob “I understand if you don't want to be my friend anymore, but please don't hate me”

“And ponies call me a drama queen It's okay, dear. I would never hate you and I would never abandon you at a time like this for such a thing. It is a natural urge that you have little control over. Anyhow ...” Rarity nervously chuckled “... it is really my fault. I should have been more considerate of you and never should have put you in such a ... compromising position”

“Thank you, Rarity. This is rather embarrassing, and quite stressful” Twilight got up and turned towards the mare

“That is understood, Twilight. It must be very difficult to adjust to a completely foreign body, with strange urges that you don't understand”

“I should have never doubted you, Rarity. You are a true friend” Twilight stepped forward and stood on his rear legs to give the mare a hug ...

... and was stopped short by a cyan magic field “I would hardly think that appropriate, Twilight, considering the circumstances”

Twilight returned to all fours and stepped back blushing fiercely “Oh!” He chuckled awkwardly “I'm sorry Rarity”

“Now, I think I have kept you long enough. I can finish the rest without you”

“I don't feel comfortable going out into town like this” He motioned at himself with his hooves

Rarity blushed slightly “You can take a cold shower in my washroom upstairs”

“Thanks, Rarity” He turned an walked halfway up the stairs

“And Twilight”

Twilight stopped and looked down “Yes?”

“A cold shower and nothing else”

“What do you mean by ...” Twilight trailed off “Ewwww! Rarity, that's disgusting!”

Here is the new and improved chapter four, the entire first half is significantly changed, but not that much has changed about the latter half.