Part One: Twilight's Machine
In the library lobby, next to the stairs that led to Twilight's room, a device was wired and prepped for usage. It took a square form and had a gaping hole in front. The sides were clear glass which could be seen through easily. Twilight was just in the middle of double checking all the circuitry to ensure no malfunctions would occur. That's when the door knocked.
"Come in," Twilight said, not bothering to take her eyes off the mechanism sitting before her.
Twilight's close friend, Fluttershy entered and asked, "You… wanted my help today, right Twilight?"
With a snooty attitude, Twilight looked over at her, and said, "Yes, you see… this device is an extractor. I'll start at the beginning, though, so you're not completely lost."
Fluttershy sat down and waited to hear Twilight's explanation. "Well… I'm all ears."
"You see," Twilight began, "I recently read a book that Princess Celestia sent me about ancient recipes that allow unicorns the ability to ascertain great doses of power within very short amounts of time. The only problem is… the recipe requires an ingredient that I unfortunately don't have yet. That's where you come in."
Fluttershy looked at her friend with a bashful expression. "But… what do I have to do?"
Twilight scratched her head before speaking. "Well… first… I need to turn you into a stallion."
Fluttershy felt her face turn into a brilliant red as she thought about the notion of having her gender bent, and by her very own friend no less. "Umm… I d-don't think… that's necessary, Twilight… Umm…"
Twilight put her reasonable mind to work in order to convince her friend it wouldn't be anything bad or regrettable. "It would only be for one day… Plus, you'd be helping me out! It'll be over before you ever even knew that it started. Trust me."
Fluttershy fought with her morals for a few moments, but eventually, she was overpowered by Twilight's confident words.
"W-well… okay Twilight… It won't h-hurt, will it?"
Twilight giggled as she said, "No, Fluttershy. It won't hurt… Actually, I'm betting you might end up really enjoying the experience!"
With this, Twilight made sure her friend was ready to commence, which after a quick shrug of the shoulders, the pegasus told her friend that she was probably as prepared as she was ever going to get. Along Fluttershy's entire being starting with her feminine hooves, an orthodox light shined magnificently, and weaved around Fluttershy swiftly as well as Twilight's horn. Fanciful sensations and an odd tingle could be felt near Fluttershy's waist and groin, and in only an instant, the spell was cast. The transformation was complete.
Fluttershy stood and sensed the presence of a peculiar, but homely growth nestled right in between her slightly quivering hind legs.
"W-what is that?" she asked before bending over to see her new and dangling body part. Resting comfortably and already thick was her dick. It had spots of yellow coloring the base followed by pink skin leading loosely all the way up to the very summit. Her head shot up and stared at Twilight with ruby red cheeks.
"That… would be your phallus. You'll want to just... sort of jam it right into this machine… yeah." Twilight giggled sheepishly as Fluttershy approached the device hesitantly. Her legs were not yet situated with this new development, and it showed. Her plot swayed as she gave a little strut forward, giving her a feel of embarrassment as her friend continued to observe.
"Uh… Twilight… You're g-going to watch?" Fluttershy asked inanely.
Twilight explained, "Well, of course. I need to keep track of just how much semen you manage to produce. Though, it probably won't be much, knowing you... No offense."
Fluttershy looked at her friend timidly to ask her, "You had to use me? But, why Twilight? Surely Rainbow would adore having… err, one of these things…"
Twilight blushed slightly and explained further in detail, "Well… the book called for the sperm of a shy, or otherwise timid mare. The type of pony actually didn't matter all that much be it an earth pony, unicorn or pegasus, but you're the only individual that I know who would qualify. The book calls it shy excess substance."
Setting her hooves on the device, the yellow pegasus continued asking her questions. "But… will I be able to make enough?"
Her equine prick aligned itself with the hole, and rested on the edge, which made Twilight's jaw dip slightly as she saw Fluttershy's measurement. It was fully erect, too. Fluttershy squealed, "Stop staring! It's making me feel weird."
Twilight looked away, and said, "Oh…. I think… you'll do just fine…"
Fluttershy looked down, and her eyes showed her unsureness. "So… do I… j-just start humping… or, just… what?"
Looking over the glass surface, Twilight thought it best to detail the mechanics that'll be at work. "The component is equipped with an auto-pressurizer. In other words, it'll do all of the hard work for you, while you get to just… well, enjoy!"
Fluttershy, blushing more than her friend had ever seen before, slowly pushed her new body part in with little trouble. The inside was extremely liquidated, but much more softer than what Fluttershy had been expecting. She gulped at the perverted tool, and despite her knowing this would probably be a pleasurable experience, she took a deep breath, but only to try and settle her nerves. Twilight then freely flipped the switch, and then, a very low buzzing noise could be heard. Right then and there, Fluttershy felt instant pleasure wash over her. She almost couldn't believe how serenely the insides were churning and cranking on their own accord. The machine seemed to know all on its own just how to sooth and gently caress the mare's now pulsating cock.
"Ah…! Twilight… Are you sure about t-this? I feel so a-awkward, letting you see me like this…"
Twilight chuckled at her friend, and explained, "I need to keep an eye on the intake you give. Too much, and you could overload the container. That wouldn't be good, and it'd ruin the carpet."
Fluttershy looked through the glass to see it beginning to fill with small droplets of precum. Looking back at Twilight, she said, "Oh… I doubt… that I could p-possibly overload it… Not that much, I don't think."
Twilight just hummed to herself while circling the contraption and keeping an eye on her friend, who was beginning to moan and twitch a little. The young pegasus's face was the most worried Twilight had ever seen. Her eyes kept blinking with every moan, and she was beginning to salivate due to the surreal amusement she was experiencing. Twilight looked at the glass once more, and said, "Anytime you need to... let it go… just go right on ahead. I won't mind one bit."
Hearing this, Fluttershy gulped once more only to reopen her moist mouth. Finally, her tender hips became tense as she felt herself suddenly blasting into the machine. Moans filled Twilight's room, and even made the purple unicorn start to blush. They weren't loud moans, but very cute sounds of enjoyment. Soon, the container began to overload. Cum spewed out of the creases which caught Twilight's attention.
"Alright Fluttershy, that's enough," Twilight said.
Fluttershy pulled out and backed away with spurts still spraying. Three nice, long lines of cum followed her exit, and then a few smaller ones before Fluttershy was finally able to halt. Huffing vigorously, she leaned against a nearby wall with closed eyes and an opened mouth.
"Wow Fluttershy!" Twilight exclaimed. "You did great! There's enough here to easily fill at least a dozen batches!"
Fluttershy's woozy head lifted itself to see Twilight's body leaned over. she busily looked through the glass with her hooves positioned at the top. At that, Fluttershy got the most diabolic idea her brain had ever conceived. Walking closer towards her friend, she said, "I'm just gonna… go lie down now…"
Twilight waved her hoof to dismiss her friend, too distracted by the extract of the pegasus's sperm to realize Fluttershy gawking bleakly at her flanks.
Fluttershy sneakily approached Twilight's lower legs, and prepared to do something she normally would never do, but something deeply compelled her. With Twilight completely unaware, Fluttershy took her chance, and held Twilight to the machine. Then, the pegasus's open hoof somehow slid right down Twilight's torso, and then her stomach.
"AH! Fluttershy!?"
The unicorn was taken off guard by her friend's sudden assault. Hoofing her snatch to keep her friend in the mood, Fluttershy explained, "Oh, come on Twilight. I saw you watching me while I was getting off on that experience. Why don't… we continue this little experiment of yours?"
Twilight gulped, and claimed, "You're not acting like yourself because of your new stallionhood… You need to stop this... now, Fluttershy!"
The pegasus disregarded this hollow warning and began eating her friend out. The feeling of Fluttershy's unwelcomed, if only impressively soft and tender tongue was weirdly arousing to Twilight. As her moans left her lips, Fluttershy stood over her, and proceeded to position her cock and prepared herself to enter Twilight's shaken, but all too moist pussy.
"P-please… Fluttershy… don't do this," Twilight said. "I'll… I'll use my magic on you!"
Fluttershy's sensitive lips nibbled on her friend's left ear to relax her before saying, "Go on, then. Use your magic to harm me… when after all, this is your entire fault that I'm currently feeling this way."
Twilight closed her eyes as her horn shimmered making Fluttershy back up. Twilight's lips drooped a bit while she took a moment to consider the intense opportunity she was passing up, and realized, "It would only be a quick one-time incident, and it's something that I haven't done before... H-have sex with a transformed mare."
Fluttershy, scared by the shimmering horn lowered her hooves, but suddenly felt them magically wrap around Twilight's waist. While she saw her friend's head turn to the side, Twilight said with a surprising amount of vigor in her tone, "Go easy on me… okay?"
The equine cock was magically sent sliding smoothly in between Twilight's lower lips. As it was moved back and forth by Fluttershy's lustful humps, her moans were joined in with Twilight's. The pegasus lowered her head down to Twilight's neck, and she began to suckle sweetly, letting some spit slide gently down the unicorn's chest. Twilight felt her friend hump at a faster pace, and while Fluttershy kept going, Twilight could hear the machine's cum swishing and burbling with every raunchy thrust. Fluttershy seemed like she had done this sort of pleasurable thing before, but Twilight herself couldn't believe her own courageous choice.
"What if…" Fluttershy began, returning to her original, shy personality. "What if I… you know… cum in you? Will you be alright with that?"
Twilight looked at her friend with a grin, and claimed, "You're actually not producing real cum at all. The substance doesn't have the same characteristics as a real stallion's sperm... So no, I don't mind cream pies one bit!"
Fluttershy continued with her rhythm as she heard this statement. Twilight's hole was much more entertaining than the machine. It was more soft, and highly inviting, and tight. As she enjoyed her pleasurable time with Twilight, her wings began to spread open which signaled her climax was at last approaching.
"Twilight… I think… I'm gonna…"
She was cut off by her friend moaning, "Do it! Just let loose and cum! S-shoot your hot, messy load as deeply as you see fit!"
The last thrust would prove to be the best for both mares. Fluttershy came longingly within her friend, almost touching the very core of Twilight's insides. Juices mixed with Fluttershy's spunk, and it all spilled everywhere as Fluttershy could hardly stop cuming. The soaked floor quickly became slippery thanks to so much jizz. Finally, when the unicorn had no more room to offer, Fluttershy pulled out, causing Twilight's hips to jolt slightly. Fluttershy, too exhausted to keep conscious, passed out on the floor, coating the right portion of her body in her own seed.
Hours would pass before she awoke in her friend's bed, clean and wrapped nicely in warm, cozy blankets.