Princess Celestia looked at the letter in confusion. Twilight Sparkle, her faithful student, had apparently taken it upon herself to solve the riddle of Equestria’s gender disparity through magical means. She had two possible volunteers, healthy mares still in their prime, and full intentions of paying, but had yet to actually inform them of everything they needed to do. Celestia knew all too well the necessity of secrecy, especially in regards to issues involving life, magic, and science, but with what these mares would be called to do, it was nearly deplorable to deny them the right to informed consent. Still, as terrible as Celestia found the idea, it may have been necessary.

“Young Twilight has given herself a penis?” Luna asked, though her tone suggested it was more of a statement than anything. Like her older sister, the entire notion struck her as incredibly odd, but well within the range of behavior she attributed to the young alicorn. The unusual methods were almost to be expected, given the extreme nature of the issue at hand, but the princess of the night was more fascinated by the leaps and bounds magic had made in her absence, if it could give a mare fully-functional phallus, along with the accompanying gonads. “I wonder why we were not told of this sooner,” she said, reading over her sister’s shoulder.

“Because, until now, it’s been impossible,” Celestia replied. “Though, I’m not sure that this is worth exploring.” She looked at her younger sister, a worried look plastered over her face. “If we can give mares this power, what becomes of the stallions we have? Will they no longer be needed?" she pondered aloud, worried that she would be exchanging a gender gap for an artificial, single-sex race. Twilight’s letter admitted her belief that this was merely a temporary solution, but there was always a chance that a larger population of stallions would fail to maintain their number once more.

“You say that like we’re on some sort of slippery slope, Tia,” Luna said, looking both amused and concerned. She knew there was a small chance that a number of ponies may think of stallions as redundant once a perfected form of Twilight’s proposed spell was made widely available, but she also knew some ponies would think that no matter what came of this experiment. “What young Twilight proposes is a chance, however slim, of finding a short-term solution so that we may then find a more suitable one for the long run.”

Princess Celestia gave her sister the letter, and pondered her options. As wonderfully careful as Twilight was, there was always the chance she would continue this avenue of research regardless of censure; it was better for everypony to have her approved to work, but under close and careful watch for any leaks, or possible misuse of resources. Twilight had two possible volunteers, and two possible subjects to pay if they consented, and while it was no big loss, it presented a unique dilemma. These two mares, both upstanding members of Ponyville society by the information provided, were essentially being paid for their services as mothers for Twilight’s possible foals. Prostitution in itself was not illegal, nor was being pregnant while selling sex, but paying a mare for the sole purpose of breeding had been illegal for centuries.

“Luna,” Celestia began, “let it be known that Twilight Sparkle’s experiments may continue.” Her voice was stern and grim, but not unkind. “Should any foals resulting from this experimentation be unwanted by their mothers or father, they may be taken as wards of the crown; a monthly stipend will be paid to their parents should they choose to keep them.” She cleared her throat and ensured her sister was indeed recording her decree. “Should Twilight so choose to continue her work, the crown must be given weekly reports on her experiments, and the health of her assistants.”

“I’m glad you have seen fit to let her continue, sister,” Luna said, binding the letter with her wax seal, then pressing Celestia’s own into a bit of golden wax next to it. She hoped Twilight would find a solution, albeit a temporary one, especially with such a bottleneck in Equestria’s future. With a flick of her magic, the letter was well on its way.

_-_-_-_-_

Twilight Sparkle read and re-read the letter a dozen times to be sure her first thoughts were correct. She could hardly contain her excitement; the approval of the princesses, no matter how short the leash they allowed her, gave her experiments legitimacy, the one thing she needed to alleviate any doubts that may arise when she informed Cheerilee and Derpy of what their job entailed. She had, by her count, forty-five or so minutes until the first interview of the day, none other than Cheerilee herself, and with the official documents allowing her research, Twilight felt she would have no trouble convincing the teacher to sign on.

She paced in the library, decidedly uncomfortable in her simple attire. It wasn’t so much that her jeans were too low-quality for her, as she’d long grown accustomed to wearing them, as it was simple restriction of movement. Spike, in his diligence, had made sure to buy her a pair with extra room in the front, but had neglected the rest of her measurements, which left her firm ass feeling as though somepony was squeezing it. While the sensation was not at all unwelcome, she much preferred the ability to walk comfortably; as nice as the denim was rubbing against her semi-hard shaft, she needed to head upstairs and change into something a little roomier, or she’d be distracted.

Once at her closet, she pulled it open to reveal a range of clothing, most of which was created long before her new attachment, so half of the items were discarded immediately. Thankfully, her top half remained relatively unchanged, but her breasts did seem a little bigger. She stripped as soon as she could, giving a soft sigh as her bra released her pert bosom; she opted not to replace it, as her breasts felt rather tender. Glancing at the clothes that remained in the possible pile, Twilight saw a few pieces that would work well, both slightly relaxed and keeping the signs of professionalism.

First, she selected a pair of opaque black pantyhose and slipped into them, giving a relieved sigh as the breathable fabric put only a bit of pressure on her, just enough for her to feel it, but not so much as to be restricting. Next, she selected a loose fitting, white blouse, a gift she’d received from Rarity that she’d never had a reason to wear; it still smelled of her friend’s perfume, despite being locked up for a few months. Once buttoned up just above her ample cleavage, she slipped on a woolen vest, one she had had for years, and was now being stretched to meet her larger physique. The vest barely covered her midriff from all she’d grown during her time as a princess, and wasn’t helped by her larger bust. Selecting a bluish-purple, thigh length skirt, she slipped her legs in and pulled it to her waist, smirking to herself as it hid her extra equipment nicely enough. Next came a matching blazer, which bore the same colours as her skirt; she eased into it, then glanced into her mirror, smiling at her reflection; anypony else would think she was heading to dinner with her brother and Cadance.

Worried she was out of time, Twilight looked to her clock, and sighed in relief; she had about thirty minutes until Cheerilee was supposed to drop in, which gave her all the time she needed to relax and unwind in her usual way: a good book. She found it difficult to focus on the pages, however, as the seconds ticked by; partly due to her own nervousness, and partly to a different sort of anxiety that stirred in her blood. A portion of her was male, and that bit was very prone to asserting itself over her right mind, especially as her body realized what Cheerilee's agreement meant. Her brain was determined to keep things civil and strictly professional until she had interviewed both her remaining applicants and gotten their answers; her cock was interested in tossing her mental processes to the wind.

The bell above the door chimed as somepony walked in, and Twilight scurried to greet them, making sure to keep her book at waist height. As if summoned by her thoughts, Cheerilee stepped into the library’s front room. She was dressed in her simple way, wearing a grey blouse and light pink skirt that reached her knees; she seemed a bit more active than most ponies were this close to lunch. Then again, she was a teacher, and years of working with foals who got groggy near mealtimes had probably trained her to take the mid-morning hunger better than most.

“Good morning, Twilight,” she said, closing the door behind her. “Sorry if I’m late; my clock’s batteries died.” Cheerilee seemed entirely genuine, so Twilight did not think she was making a joke about her punctuality. “I’m not too late, am I?”

“No,” the princess replied, “you’re actually about ten minutes early.” Cheerilee breathed a sigh of relief, glad the opportunity hadn’t been missed; fifty bits per day was nothing to scoff at. Only the most dangerous of jobs offered that much, but for something as simple as a lab assistant, it seemed nearly too good to be true; Princess Twilight must have been in a generous mood to offer a position with that sort of salary, especially for the amount of physical labor the ad hinted at. “Well, might as well get started. Please, take a seat.” The school teacher did as asked, yet the town librarian remained standing. “Now, I’m sure you’ve noticed that there seem to be more mares than stallions.”

“Well, there are more fillies than colts in my classes,” Cheerilee said, thinking back to her own graduating year. She remembered ten stallions in all, the same ten she’d known her entire life, the same ten she started school with; there were never any more, nor any less, than those ten. She had never paid it much mind, but it did seem a bit strange when she factored in what she knew of probability and punnett squares. “I’ve actually always wondered why, though.”

“You and most of the scientific community, actually.” Twilight put her hands on her desk and leaned forward, basic body language to let Cheerilee know what she was saying was to be taken seriously. “For years, decades, perhaps longer in an unofficial capacity, ponies have been trying to find a solution. Dozens of breeding programs have failed to stabilize test populations, and we’re basically back where we started.”

“But what about that colt-only spell?” Cheerilee asked. The spell itself was common knowledge, and available in liquid form for use by non-unicorns, so she wasn’t too sure why the numbers still weren’t even. “I mean, it works, doesn’t it?”

“Oh, it works just fine, but the number of stallions available for breeding is still too low,” Twilight replied, bringing a book from under her desk. For a moment, the teacher felt a bit guilty for interrupting her reading time, knowing the princess’s bookworm tendencies. “Even if every stallion sired three colts, the only thing it would cause is a massive linking of Equestria’s family lines.” She ran her hand through her mane and sighed. “After a few generations, inbreeding would be worryingly common.” Twilight reached for a folder, and slid it to Cheerilee for her to see. “Numbers have been crunched, and as unbelievable as it seems, ponykind may well be doomed in the long run unless a better solution is found.”

“And you’re working on a solution yourself?” the teacher asked, putting a few pieces together for herself. When Twilight nodded, she thought she’d figured out some of the princess’s secrets, the reasoning behind the vague advertisement and odd testing done during the application process. “So, what sort of experiments will I be helping with? You know I’m not exactly a biologist.”

“What I’m proposing is, well, a tiny bit illegal,” Twilight said, trailing off at the end until her voice was only a whisper and she sulked in her seat to avoid whatever negative reaction Cheerilee might have had. “But, the princesses have given me their approval, and we’re exempt from the law for the time being,” she added, quick to prove she wasn’t going to be making Cheerilee a criminal any time soon. She showed the teacher the scroll bearing her signed pardon, but kept the content concealed for the time being. “The goal is to reliably produce stallions, so, I needed the assistants as volunteers.”

“Produce… stallions? So what, are you asking me to volunteer myself as a surrogate to some random stallion?” The entire notion was more than enough for Cheerilee to prepare herself to walk out the door if her host failed to explain herself. It took only a moment for Twilight to stand, pushing her hips forward as she did so, and creating a rather noticeable bulge in her skirt. The teacher looked at it, then the princess’s face, then back to the distortion of cloth in question, before finally finding the nerve to speak her mind. “Is that a… dick?”

“Yes; I couldn’t just get any random stallion for this,” Twilight answered, lifting the hem of her skirt to reveal her stallionhood. “Like I said earlier, using existing stallions will result in a bottleneck, but if we can find a way for mares to produce colts using only their own genes, then the issue is handled.” The princess saw the stunned look on Cheerilee’s face, and quickly hid her organ behind the curtain of her skirt to avoid causing her any more trauma. “Again, you can say no if you wish, but I must ask that you maintain total secrecy about what you’ve seen if you decide to walk away.”

Much to Twilight’s disappointment, her possible volunteer seemed to take her up on the offer to leave, standing as she made to walk away. It was only after a moment that the princess realized she was actually walking towards her instead of the door. She jumped as the shorter mare’s hand came to rest over her shaft. “I’ve heard of some mares using spells like this, but always heard they only fired blanks.” Even as Twilight tried to remain scientific about things, she couldn’t help but tense as Cheerilee kneeled to better level herself with the object of her curiosity. “You think this,” she began, fondling over the length of rigid flesh held tight against the princess’s thigh, “can do what others can’t?”

“I-in theory, yes,” she replied, shivering under the foreign touch. She had barely grown accustomed to her own hand, much less that of another; she was beginning to think she’d bitten off more than she could chew by taking on assistants so soon. “But, we don’t have the proper equipment up here; all the insemination instruments are in my lab.”

“Oh, I’m sure we can make do if we go upstairs,” Cheerilee said, grabbing Twilight by the hand and beckoning her forward. Though originally apprehensive, the idea of a good fuck was starting to grow on her, and despite, or perhaps because of, the oddity of the situation, she found herself nearly as aroused as the princess seemed to be. “If you’ll show me to your room, I’ll show you how natural insemination can be much more enjoyable than your clinical process.”

Twilight, unsure of what to do, led the teacher upstairs to her room. With surprising ferocity, Cheerilee pushed the alicorn onto her bed, quickly climbing over her laying form. Sliding a hand up the princess’s skirt, the earth pony massaged the hard length through her pantyhose, locking eyes with the cock’s owner; she licked her lips as she thought about all the wonderful things she’d do. With a quick glance up, Cheerilee rolled away and moved to the head of the bed, smirking at what she found just barely within sight of her earlier position. “Interesting. Are you helping the local Filly Scouts with their knot work?”

Twilight’s cheeks lit up with embarrassment as she saw the lengths of rope Cheerilee had gotten ahold of, but remained still as the earth pony grabbed one of her arms. “C-Cheerilee! W-what are you doing?” In no time at all, her wrist was tied to the bedpost; Cheerilee remained silent, but obliged the cocked mare with a grin. Rolling over to the other side of the bed, the teacher found the first rope’s twin, and did not hesitate to bind the alicorn’s free limb. It was simplicity itself to finish the job, and she made use of another pair of ropes to fully restraint the princess, tying her legs to the last posts. Blushing furiously, but not resisting, Twilight looked down at the suddenly-ravenous mare. With her elbows resting on the bed, Cheerilee met her gaze from between the princess’s legs, and finally spoke.

“Well, we might as well enjoy it, right?” she asked, pulling Twilight’s pantyhose down. The cock the thin fabric once held in check bobbed free, throbbing with every beat of its owner’s heart. Cheerilee gave the shaft a gentle stroke, and had to suppress a laugh as her captive’s legs trembled. “Hmm, this should be fun,” she said in a purring, sultry tone. She gripped the princess’s cock tighter, and had a realization as a whine peeled through the air above her. “Are you not used to having this, your highness?”

Twilight winced at the sensations, and shook her head; it was the honest truth that she had little call to touch herself with anything other than her magic, and her hand was a fluke brought on by arousal she hadn’t experienced much before. Her eyes, once closed as she fought to maintain her composure, shot open as something warm and wet dragged over her shaft, flicking over her tip as it came free. Cheerilee's lips curled into a smile as she open her mouth, a hungry glint shining in her eyes; Twilight realized what the teacher intended, and braced herself for it.

Amazingly, she did not lose control as Cheerilee took her cock into her mouth, though those warm confines and her swirling tongue were more than enough to sap any tension from her trembling legs. Very slowly, the older mare bobbed her head, taking her time to either torture her captive, or prolong her own pleasure; Twilight didn't care which, so long as she kept it up. Something brushed against her nethers, and the princess whimpered as a probing finger slid in. Cheerilee’s digit massaged as it explored, gently rubbing prodding at every crevice it could reach.

“I’m r-really sensitive,” Twilight gasped out. Her cocked pressed against the back of the teacher’s throat, and Cheerilee flt that was the best time to start humming. Her breath hitched as her stomach cramped, and she only had time to slap the mattress once or twice before she lost control. She looked down in time to see Cheerilee’s eyes widen as the first rope of cum shot in her mouth. The teacher pulled back until only the tip was still in, and closed her eyes as she swallowed as much of Twilight’s warm seed as she could.

For a moment, she wanted to apologize, but seeing Cheerilee’s grin kept her from saying anything meaningful. Cheerilee stood and took a step back, sucking the finger she’d used on Twilight, while her other hand was busy under her own skirt. She looked excited in a way Twilight had never been, or at least recalled herself being, and if the princess considering going soft, that look made her cock think otherwise. The earth pony slid her panties down, stepping out of them as she twirled them around a hooked finger. “Take a good look, princess,” she said, stretching the article out so Twilight could see them better. They were soaked through, and she could nearly see Cheerilee’s face behind the semi-transparent fabric.

Slowly, the teacher climbed over the bound princess, straddling one her legs and letting her moist lower lips soak into the lavender fur under the sheer hosiery as she slid up to the alicorn’s crotch. She moaned as the fabric rubbed against her nethers, looking into the princess’s eye as went. Cheerilee lifted off her leg and lined herself up with Twilight’s cock, idling down until she rested on the shaft, pressed between her pussy and the purple mare’s stomach. “Open wide, your highness,” she said, holding up her balled panties.

“Why?” Twilight tried to ask. Instead of voicing her question, her words were muffled by the sudden gag of soaked cloth; though as soon as Cheerilee’s honey hit her tongue, she lost all will to object. The teacher was sweet with a tart edge, a flavor that spread through her entire mouth and sent shivers down her spine. She could have removed the improvised gag any time she wished, but for the time being, she was content to see how things played out. Cheerilee smiled down at Twilight, lifting her skirt to show her soaked nethers, and raised herself off the princess’s cock.

The teacher didn't say a word as she slid down, easing the alicorn's stallionhood in; she relished in the sensation, so much better than anything a toy could provide. Biting her lip Cheerilee looked down to see how much she had taken in,and smirked as she saw how much of Twilight’s cock she still had left to take; just over half of the hard shaft was still waiting for its chance to be held by her. The earth pony braced a hand against the princess’s chest to steady herself, careful to maintain her altitude; she made good use of her flexing muscles, contracting over the dick she so loved to tease, and loving every twitch and murmur Twilight made under her. “Does that feel good, princess?” she asked, sliding her hips forward. The alicorn went to spit the panties out, but Cheerilee placed her other hand over the lavender mare’s muzzle. She leaned in close to whisper, her voice barely audible, but stern and entirely commanding. “Just give me a nod.”

A new wave of excitement through Twilight as she nodded, desperately wanting to be deep inside the mare straddling her crotch. She tried to move deeper, Cheerilee moved away just as much, wagging a finger in the princess’s face. “Did I say you could move, your highness?” she asked as the alicorn whined and shook her head. “Go on, back down with you!” she commanded. Giving a muffled whimper, Twilight did as instructed, laying back and pulling away until only her tip was still making contact. She silently pleaded with Cheerilee not to torture her much longer; as much as the princess wanted it to be untrue, the teacher’s pussy was infinitely better than her own hand or magic, so much so that the only reason she hadn’t cum again already was her earlier orgasm.

Twilight’s eyes shot wide open as Cheerilee thrust herself down, taking all of her length with ease, struggling as she tried to bite back a ragged gasp as she felt her entire stallionhood swallowed by the slick, tight tunnel. The teacher panted as she got used to the feeling of a real cock once more, regretting only that she had not started this so-called experiment sooner; she’d made do with toys and her own imagination for far too long, and she was going to enjoy riding this mare for all she was worth. Cheerilee rose and slid back down, moaning as she felt nerves long left unattended spark to life. She began to speak, but jerked to a halt as Twilight shot a glob of pre that burned a warm trail as it joined the rest of their mixing fluids. “Consider this my signature,” she managed to say, almost too caught up in her own pleasure to bother.

Everything about this was perfect in the teacher's mind; she had a pretty, younger mare tied to a bed as she rode a hard, hot cock into bliss. Cheerilee leaned back to angle Twilight's stallionhood against her front wall, bracing one hand on the mattress behind her as she bounced on the princess’s rod. Smiling devilishly at the look of blissful pleasure on Twilight’s face, she realized her captive royal may not last much longer. Eager to speed up the process, and hoping to see the librarian’s face in agonizing rapture, she thrust her free hand behind the princess’s sack.

Cheerilee plunged two fingers through Twilight’s soaked lips, effortlessly gliding into her spasming pussy. The alicorn writhed and bucked against the stimulation, thrusting wildly against her captor in an attempt to maximize her own enjoyment. The princess’s breath caught in her throat as her stomach started to cram up, giving her only enough time to let out a strangled, muffled groan as her body slipped from her own control. Twilight pushed as deep as she could, burying herself to the hilt as she came. Cheerilee had different plans.

The teacher pulled herself off the librarian’s cock in time to aim the first shot of cum; with a twitch of the alicorn's cock, a rope of her thick seed splashed across Twilight’s muzzle. The next burst went higher, landing on Twilight’s eye and mane. The next globs stained her clothes as they hit her body, still copious enough to hint ooze and spread across more of the purple fabric as it soaked in. The last shot, the weakest and thinnest, landed in Cheerilee’s hand, who cupped it in her palm. “Oh, princess, don’t think we’re done just yet,” she said, massaging the cum she held into the head of Twilight’s cock.

_-_-_-_-_

Spike sat in the foyer, as he often did when Twilight was busy; he only knew she was busy because the book she’d been reading was still open on her desk, and she was nowhere to be found. He took that to mean Cheerilee had accepted, and he believed they were in the basement running fertility tests and other such things he didn’t want to think about. For him, a young dragon well into his teens, sex was something he desired in copious amounts, though all desire left when his adoptive sister was the object of his thoughts. Thankfully, in line with the dubious legality of the experiment she would be assisting Twilight with, the library’s main rooms were soundproofed from the rest of the house, so nopony browsing for books would be disturbed in any sense of the word. Like many teenaged stallion, he passed his time of boredom and tending the library with a few chapters of a science fiction novel he’d found in the basement.

A knock at the door grabbed his attention; he checked the clock and realized the time for Twilight’s second appointment of the day was quickly approaching. He marked his page and stood, adjusting his jeans as he walked to the door; it would not do for his ants to fall down as he greeted the second possible volunteer. Straightening his shirt, he opened the door, unsure of what sort of mare Twilight had found; he partially expected some local waitress or something, somepony down on her luck who needed the money and didn’t mind the possibility of going to jail. What he saw as he opened the door was far from his expectations.

Grey-furred and blonde, the mare stood a bit taller than he did. She looked at his with yellow eyes, and smiled warmly. She was older than Spike, that much he knew based on Twilight’s requirements, though her age did little to subtract from her looks. This mare, a pegasus by the wing on her back, was like many of her kind: she was lithe, with thin thighs and a small frame. Her hips and bust were larger than most pegasi, more in line with unicorns than one would expect. She wore a form-fitting, grey uniform that matched her coat and bore the patches of a postal worker, though her name tag was noticeably absent.

“Hello there, I’m Derpy Hooves.”

Author's Note

Right, so my good friend Lucky424 helped me write the sexy bits, and I feel obligated to pass some praise his way.
Check out his story, The Conquering of Pride, for Twixie BDSM action, to be updated within the next 48 hours.