Cutie Mark Crusaders, Spell Testers!

There was much um-ing and ah-ing as the trio came to terms with what they were just shown and what they were about to have done to them. Sweetie Belle shuffled on her hooves anxiously, always thinking of herself as a prim and proper lady, while Apple Bloom drooled and tried to sneak some more peeks at Twilight's new gear. Finally, Scootaloo raised one hoof and stepped forward, her wings twitching with anticipation.

In the middle of the library was a horizontal bar supported on two poles, each of which had multiple notches in them for placing the bar at different heights. “Alright then, just put your forehooves up over the bar and relax." Twilight instructed. "I should warn you this spell's a bit more intimate than you may be used to. You might feel a slight prickling sensation... Ahem, so to speak!”

Scootaloo did as she was told, and after some minor adjustments, her head was lifted in a position that was both comfortable and gave Twilight - and the other two Crusaders - a proper view. A purple glow surrounded the space between Scootaloo’s budding teats and her virgin pussy, heating the air around her groin as though a cloud of steam was gathering underneath her. The blob of arcane energy pulsated around in a massaging motion as Twilight sharpened her focus. She needed time to warm up - after all, this was only the second time she'd tried manifesting a new manhood. The massage also served to relax Scootaloo in body and mind, making her more susceptible to the changes. She closed her eyes and took deep breaths as two small bumps started to form just above her clit. Pressure built within as these new orbs swelled inside her body, almost painfully, like a stomach cramp. Once they reached a sufficient size Twilight used her magic to stroke downward, stretching the flesh out to make a roomy pouch for them. Her wings shuddered with shock and pleasure when her still unfamiliar testes slid into their new home with ease. This sack, her ballsack, was practically devoid of fur, exposing her mahogany brown skin.

“Mhm, I see, I see.” With magic still pulsating around Scootaloo’s nethers, Twilight quickly marked down some notes on her clipboard. “All working as expected so far! Any questions?” Scootaloo and Sweetie Belle shook their heads, while Applebloom continued to watch intently with envy. The balls now in place Twilight continued swirling her magic around them to refine their shape and size.

All the while Scootaloo was feeling increasingly horny. The ethereal cloud of magenta running across her skin felt amazing, like a loving mother's tongue. She bit her lip in a vain attempt of stifling a moan, but the soft squishy sounds of her clit's rhythmic winking betrayed her. Twilight smiled. "Perhaps it's working a little too well. I think the more intimate nature of this casting method may be a little much for a filly." She jotted down some more notes as she continued.

"This is a little technique I picked up from Zecora called fleshcraft. It really helps to define all those nooks and crannies," she said as she added a small crease to the center of the sack, defining the pendulous balls in their separate chambers. She continued to infodump about the magics at play as she worked. "Normally this would be done with a cream of some kind, but the alchemical processes of zebra magic adapt quite easily into the unicorns' arcane techniques. And the best part is that it takes the wants of the target's subconscious into account as well as genetics, so not only can it provide more customization, but there's also less chance of funny business from the caster. It's very much a spell for pleasure, as opposed to most transformation magics which were designed for the sake of quick disguises or incapacitating enemies."

Twilight rambled on, ignoring Scootaloo's quickening breath and loudening whimpers. As the volume increased it became harder to brush off, though, so she decided to check in. "How do you feel about this so far? Need me to stop?" Scootaloo shook her head again as her wings quivered. With a final flourish of magic swirling around them, the pair of balls settled into a modest chestnut size, fairly average for a colt of her age. When the magic receded, her balls immediately became rather cold, and just as quickly as they descended, the skin tightened around them and became smooth. "Alright then," Twilight grinned. "Time for the main event."

Twilight's magic swished up to where the ballsack connected to the groin and formed a ring just ahead of it. It glowed brighter and swirled around the ring, leaving a trail of light and gradually extruding out a sheath. She knelt to the floor and stuck her head under the filly's belly to get a closer look at her work. Immediately she noticed the sweet and savory odor of a stallion ready to rut wafting around her head, emanating from Scootaloo's balls. "Woof..." Twilight said under her breath, immediately clearing her throat to obscure the embarrassing utterance. The air was thick with heavy musk, and she couldn't hide the effect it was having on her as it assaulted her senses. Scootaloo must be in heat - she thought - perhaps her first. She hoped this temporary alteration to her sex wouldn't interfere too much and embarrass the filly, though at the same time, it would be valuable for scientific inquiry. The sack had quickly developed a sheen of sweat which highlighted its contours, and Twilight couldn't help but take pride in her craft. Or maybe that was just her arousal from taking in the intoxicating scent. Regardless, she quite liked the look of them. "Ahem, i-it's a lot like pottery, you know." She said in a vain attempt to distract herself. "Perhaps you should try getting a cutie mark for that too if spell-testing doesn't work out"

Scootaloo's head vibrated up and down in agreement as she struggled to reply. "Mm-m-ayb-be!"

The shaft continued to come out, and as it did, an unwavering erection revealed itself. A deep mahogany brown, nearly black, Scootaloo's new member was on the average side for a colt at around 8 inches. It was a little bit thin, but the way it flared out more than made up for that. As of yet though it was a perfectly smooth rod of meat, lacking much of anything to make it a proper dick. Twilight's magic ran up and down the length sensually to remedy this, incidentally jerking her off in the process. She got to work on adding features, starting with the medial ring. Scootaloo started to buck into the glowing ring, hind hooves tapping on the hardwood floor as she tried to contain herself. Her new cock started to pulse wildly, Scootaloo slapping it against her belly. Twilight knew what this meant, but made the mistake of thinking Scootaloo could hold it. Ignoring the twitching she persisted and got to work on shaping the tip.

Suddenly, it all had to be let loose. As the finishing details on her flare were being added - the most sensitive piece - Scootaloo had her first orgasm as a futa filly. She suddenly thrust forward and drove her cock up the bridge of Twilight's nose, leaving her balls right at her nostrils and forcing her to huff their scent. Thick ropes of cum squirted out without warning across Twilight's face. They streaked in her mane and splashed all over her fur. She had to close one eye quickly to avoid a shocking sting, and a few strands dangled down over her snout. The unicorn's face took on a shocked expression, mouth agape, but it was quickly replaced by a smile trying to suppress giggles.

Scootaloo, however, was mortified. "I'm so sorry Miss Twi!" She slurred out in her post-nut haze. Her cock was still pushing out the last of its semen, pulsing up and down and tapping Twilight on the nose. Still yet, more cum dribbled out straight into her fur.

Twilight licked her lips of the virile seed before she levitated a nearby hoof towel to wipe herself clean. She was prepared for this to happen with at least one of them, but she wasn't expecting it to be so hot! The taste of Scootaloo's cum lived up to the smells - salty, sweet, and smooth. She was getting dizzy with lust and couldn't help herself much longer. "D-don't worry about it, I know from experience this procedure can be a little intense! Here, let me get you cleaned up." Without giving Scootaloo the opportunity to question what was to happen next, she took her shaft into her mouth from the side and slid her lips up the length. This coaxed out the last drops, which she resisted consuming to instead capture in a vial for later research. Scootaloo nearly collapsed - she would have were it not for the beam she was held up by. "Mmm, good girl, you've been a very good test subject!" Twilight commended the filly as she let her off the bar and sent her back to her friends with a slap on the rump.

"So, who's next?"