Mary groaned as the Kentucky Golden thundered past the finish line, three places ahead of her horse, State Ticket. The brunette combed a hand through her curly hair with a loud sigh, turning to Harriet and finding an eager grin on her friend's face.

Mary owed her money, and though it wasn't an excessive amount it was enough for a drastic double-or-nothing. Of course, as with most of such things, it didn't end in her favor, and now Mary was looking at an oncoming TransFun serum. A horse serum, specifically.

“Well, one way or another you're clearing your debt.” Harriet, the daughter of the track's owner, winked with a chuckle in her throat and a smile on her lips. She'd booked an empty stadium for the next few hours, ensuring she and her friends would be able to ride off Mary's debts.

“Yeah, yeah.” Mary groaned. “I'd have rather paid it off without working, though...” She sighed and crossed her arms, tapping her foot idly. “So, when are we going to do this?”

At that, Harriet smiled mischievously. “Follow me.” She turned and headed back to the private rooms of the track, loudly humming 'Camptown Races'.

Mary sighed and rolled her eyes. “And here I thought you couldn't wait for me to get a little mare-y.” She called loudly back, hearing the musical sound of Harriet's laughter.

“Oh, I can't. But first things first, we need to get you in a proper outfit.” The girl called back, a grin on her face.

“Um... What?” Mary blinked, rushing up to her friend. “What outfit?” She asked.

Harriet's response was to open the door to the private room before them, revealing a smiling young woman with dazzling red hair.

“Hi, Molly.” Mary groaned as she recognized her seamstress friend. No doubt she had a hand in this 'outfit' which Harriet was talking about.

The redhead's smile widened as she looked Mary up and down. “Yeah, you're perfect for this!” Without further ado, she pulled a riding outfit out of the bag behind her, her eyes twinkling.

Mary stared in shock, looking back to Harriet with no small amount of confusion. “You want me to wear this when I transform?”

Harriet clicked her fingers. “Right in one. Molly and I were thinking of going into business together, making rippable clothes. And who better to test our first outfit than our very own guinea pig—or horse, as it were.”

Mary blinked in surprise. “That's... Actually not a terrible idea. Is there any room for a third founder in this little business venture of yours?”

Harriet laughed. “Try asking again when you don't owe me any money.” She winked at the brunette, sipping out a TransFun serum. “You still know your way down to the tracks?”

Mary nodded, taking the little glass vial in her hands. She looked up to find Harriet leaving the room, waving behind herself.

“Then meet me there once you get changed. I've got to make sure you don't have an audience for your transformation.”

Mary sighed and turned to find the redheaded girl grinning at her. “We're going to have so much fun today!” She squeaked happily.

“Yeah... Fun.” Mary muttered unsuredly, slipping off her clothes to get into the handmade outfit.

To her surprise the riding gear was quite comfortable, and actually very soft. She voiced her praise to the seamstress, who blushed happily as they headed down to Harriet.

“Well, I wanted to make sure as light of a fabric as possible, ensuring that your tearing through your clothes won't hurt you at all.” Molly grinned. “That said, I couldn't do that for everything, so for the tough things like your shoes, I had to add some fault lines for the rips to begin across.”

“That would explain why my feet can breathe so easily.” Mary nodded with a smile of her own, wiggling her toes within the leather boots. She adjusted her cap anxiously as she walked, ready to face the oncoming change.

Harriet greeted the two of them with a smile on her face and a wave to the track around the trio. “Completely empty, for your consideration.” She beamed with pride.

Mary smiled thankfully and uncorked her serum. “So I take this and we're square?”

Harriet nodded. “That's the idea.”

“Then bottoms up.” With that, Mary gulped down the liquid, an earthy taste left on her palate as it rushed down her throat.

Her heart started to pound with anticipation at the oncoming change. She'd never transformed in clothing before; this would be a completely new experience—maybe one that was a little deviant.

Though animals had no need for clothes, she was still a person deep down. The thought of them bursting around her and leaving her naked was a little risqué, to say the least.

“How do you feel?” Molly asked with a smile. “Clothes too tight? Too loose?”

Mary chuckled, looking to the redhead with a grin on her face. “No, they're perfect. I'm just waiting for the chu-uh-anges to start.” The girl blinked and tossed her head instinctively as her voice quavered slightly, an equine nicker leaving her mouth.

Harriet beamed. “I've never seen a serum go voice first!” Her smile widened with anticipation, her stare making Mary feel a little uncomfortable.

“Me nuheee-ther.” Mary blushed, a warm feeling trailing across her cheeks. Then the feeling started to itch, and with a  faint yelp the woman realized that she was beginning to grow fur.

“It's itch-eee!” The brunette hiccuped, her fingers moving to itch at her skin beneath her riding gloves. She tossed out her head again as she scratched, her curly hair straightening behind herself.

The warm, itchy sensation trailed from her cheek to the sides of her neck and Mary continued to scratch at herself, nickering slightly with discomfort.  But with each scratch of her fingers, it became a little harder to move them, a little more difficult to curl her digits.

The realization hit Mary like a splash of cold water, and she looked down to her hands to find that her gloves were starting to bulge with the growth of what could only be hooves. With that, she slipped them off, discarding them with a small grin.

“Suh-horry Molly, wuhhhant tuh suheee! Hooves!” She gasped, looking down at her hands as they went numb, her skin bulging despite the lack of sensation from around her palms. Mary let loose a slight yelp of surprise, watching as her fingers darkened; becoming thick black sausages on her hands. She touched the ones on her right hand to those on her left, hearing a clacking sound not unlike two pool balls making contact.

“This is suh-huh-huh-real.” Mary nickered, watching in surprise as her fingers began to merge, forming large and dark hooves where her hands once were. Then a feeling of dread hit her as she realized that without hands, she could no longer scratch at herself. It was like remembering a bug bite: suddenly her whole body began to itch, and Mary whimpered, pawing at her form with her useless hooves.

“Feeling a little itchy, are we?” Harriet grinned, elbowing Molly.

The redhead yelped in surprise, then added a comment of her own. “Maybe it's less that you're itchy and more that you're just now realizing how uncomfortable your clothes are!”

The thought lanced through Mary's brain, and she realized that Molly was right: her clothes were the primary source of this discomfort. Her fur was itching so much because it was being pressed against her riding outfit! The girl whimpered and nickered as she tried to paw at herself to undo the buttons on her shirt.

But a new sensation forestalled her efforts just as they'd begun. Mary froze as her feet went numb, just as her hands had done moments before. The girl's heart raced as she looked down to her boots, just as eager to see her hooves burst free as Molly was. Her stupid hooves kept her from kicking them off—yet there was something about the prospect of watching her feet free themselves that she just couldn’t shake.

As though sensing her desire to witness the changes, her neck transformed as well, lengthening and thickening into a proper horse's collar. The seams along her shirt tightened, but Mary paid them no heed. She wanted to see what was happening to her feet!

Sure enough, they were beginning to bulge, the onset of hooves stretching out the tough leather of her boots. Small tears formed along her footwear, and Mary nickered with eager anticipation at the thought of her feet bursting free of their confines.

Not being able to see them change somehow only made the transformation that much more alluring! She could feel her toes withdrawing into the calloused lump that was a forming hoof; hard enamel sweeping over her flesh to protect it and let her thunder along the track with ease.

Mary could feel her feet stretch out even as they shortened back upon themselves, seeing the effect of this bulging on her boots. Then, with a loud tear, her feet burst free, letting the woman see what was left of her toes shrink back into the large and round hooves that now marked the tip of her legs.

She took an anxious step forward on them only to wobble sightly. It was a lot like wearing pumps, if pumps also cut off your toes. “Nnh-it's huuurd tuh wuhalk.” Mary managed, forcing the words out through her longer neck.

She didn't realize how hard it would be to speak with a horse's neck: she thought that with her mouth intact, forming words would be a piece of cake. Instead, her every syllable had to struggle through a thick and phlegmy throat that seemed desperate to impede her speech as much as possible.

“Well, why not fall to all fours?” Harriet asked with a grin. “We all know you'll end up on them anyways.”

Mary shook her head. “Nuh-nuheeigh!” She whinnied, her arms windmilling for balance as her torso began to expand. The brunette had to squeeze her eyes shut in discomfort as the transformation undermined her attempts to remain bipedal.

It was like she was gaining hundreds of pounds, all of them muscle! The girl's trunk barreled out more and more, getting larger and larger by the second. Her poor legs could barely support her weight, and her damnable clothes were so tight on her body!

Then her shoulders popped, throwing her arms forward and increasing the pressure of the clothing around her back to its limit. With a loud tearing the seams began to give way, loudly heralding Mary's descent in to a quadrupedal stance.

“Nuheeigh!” Mary neighed, trying to deny the fact that she was falling onto all fours. She wanted to spend some more time on two legs, darn it! But the transformation wasn't listening to her, and with a loud thump the girl landed on her hooves. She quavered with sensation, an impossibly strong urge washing over her body; a need to run and run and run.

This came just in the nick of time, as her hips popped next, fixing her legs in a new and horsey position. Had that happened when she was still bipedal, her fall would likely have been a good deal more painful. Mary snorted with distaste, shaking out her body and feeling her jacket begin to tear a little more around her barrel of a torso.

“All right, so the coat works!” Molly squeaked with pride as Mary's body expanded a little more, shredding her jacket. “Now to see if the pants do the same.”

Mary's eyes widened and she looked to her rump in surprise. She hadn't expected that! Sure enough, her pert butt was swelling by the second, straining the white cotton of her breeches.

The girl huffed in amusement as her backside grew ever larger, looking back up to her friends with a mischievous smile. “Huh-uhorrse butt.” She beamed with amusement, wiggling her backside behind her.

The motion was enough to send her pants over the edge as well, and they loudly tore around her backside, their shredded pieces falling gently to the ground. Mary nickered contentedly as the feeling of discomfort she now associated with clothing passed over her, and she grinned back to her friends.

The smile lasted for only a second, however, as Mary soon realized that her rump wasn't the only thing to begin to grow. Her cap was feeling awfully tight on her head, and with a loud nicker of surprise, Mary realized that her skull was beginning to reform.

The strap under her chin was tight; too tight! Mary tossed her head to and fro, her eyes squeezed shut as she tried to force the cap from her head. She could feel her ears lengthening, trying to slide up her head but unable to do so while she still bore the rider's cap.

“G-uhnn! Guuht utt uhfff!” Mary groaned loudly, tears forming at the corners of her eyes as the strap dug deeper into her flesh. Then her jaw began to expand, and a loud snapping accompanied a flood of relief through Mary's head.

She tossed her head from side to side, feeling the cap fall to the ground. Relief made her shoulders sag, and Mary looked up to see Harriet holding Molly back, a smile on the track-owner's face.

“Sorry about that, but it's not a real test run if we run in to help you at every opportunity.” Harriet called.

Molly seemed to be half-hysterical, her cheeks as red as her hair. “I'll fix that strap next time, I promise.”

Mary snorted, her nostrils expanding. “Yuh-oo'd buhutturr.” She grunted through thickening lips, her mouth beginning to grow. The girl nickered again as her nose and jaw pushed out to a muzzle, her teeth and tongue expanding within its roomy confines.

She tried to speak again, but only a neigh came out. Mary rolled her eyes at her inability to communicate, only to neigh again as her eyes began to ache. Her vision degraded as they began to widen, and with a faint groaning within her skull her eyes slid to either side of her head, offering her a wider view of the world around herself.

Mary was so shocked by this that she barely even noticed her spine lengthening into a tail behind her; her arms and legs stretching out around the shredded remains of her clothing. Instead, she swiveled her head around, looking at the world through a completely new perspective—and hearing it from one too!

She didn't know how she'd missed it, but Mary could move her ears independently of her body! And her nose—the bouquet of smells was like nothing she'd ever experienced.

“So, aside for the cap... Would you call this a success?” Molly asked, intruding on the transformed girl's thoughts.

Mary nickered happily, realizing her transformation was completed. Then she answered Molly's question by covering her cheek in a big and horsey lick.

The redhead squeaked and Mary huffed contentedly, trotting in a small circle and marveling at how much more powerful this body was. She actually wasn't sure if she'd lost the bet anymore—this felt like a real winner of a day!

“So, now that our debt's been settled... How about earning some money at the track instead of losing it?” Harriet winked at her friend. “Let's see how good of a racehorse you are. Who knows? Maybe if you earn enough in the races, we'll see about making you our full-time clothing tester.”

Mary's eyes widened; then she snorted loudly with amusement. She wasn't so sure about the last part, but the former statement was a challenge that her equine body was all to willing to meet.

The newly-made mare trotted to the starting line, ready to see just what her new body could do.

“On your mark!” Harriet called.

Mary huffed and flicked her left ear to acknowledge the girl, focusing on the track before her. This was it, the point where she truly made today from a loss to a victory. Her equine body was stop powerful, nothing could stop her.

“Set!”

The mare tensed, her ears held back against her head as she flexed her legs.

“Go!”

With that, she was off, thundering forward in a charge that would define the turning point in her life.

 

The woman changed back a few hours later, a slow change back to human that had still left her with equine ears. She flicked these with interest, grinning back to her friends. Her heart was still racing; she couldn’t help but want to do it again! As a matter of fact… “So… Now that I’m sold on TransFun, what’s next? That can’t have been all we needed to make up my debt, right?” She nickered softly, an aftereffect of the transformation.

Harriet smirked at her friend, petting her behind her horsey ears. “Well, if you insist… We do have a few ideas…”