Shining eyed his reflection in the mirror with a soft, almost dreamy sigh. The image of a pretty mare, slim, dressed to the nines, smiled timidly back at him.

He drew both hands up his hips, noting how well his fingers seemed to taper into his waist as the soft pink cloth of Cadance's panties shimmered over his crotch. His thumb brushed against the bulge his package made in the gentle fabric, sending a shiver up his spine. When he pulled his finger away, there was a spot of moistness on his fur, and a good-sized damp spot on the panties themselves. Shining sucked the warm pre off his thumb, and moaned softly as he felt his member stirring to life in the tight, feminine confines of his wife's lingerie.

A bra covered his toned chest, looking absolutely ridiculous over his slim pecs. His six-pack, though not bulging, didn't look feminine in the slightest, and the way his biceps flexed would have left no one believing he might have been a mare. Still, Shining couldn't help but feel a spark of excitement as he traced his fingers, imagining them to be long, slender, delicate like a mare's, up the thin fabric of his patterned leggings. A blush colored his cheeks as he eyed his reflection in the mirror, his hips swaying gently from side to side like a nightclub dancer's.

He gave his package a light pinch, and moaned softly as his hips bucked on pure reflex. Another glob of precum erupted from his lengthening erection, the damp fabric elongating across his girth with each inch his organ swelled. He swayed unsteadily, watching his hardening member bob lazily against the tight confines of his wife's panties, the lacy, delicate fabric looking almost about to tear as the rock-hard girth of his lengthening organ pushed them ever-further away from his crotch.

Strictly speaking, Cadance didn't entirely know that he was doing this. She was out at a meeting now, actually, but a horny Shining had seen the opportunity to fulfill a secret kink—and without the fear of being found out by his wife's watchful eyes. He cupped one of his balls in his palm, savoring just how big and full it felt in the confines of Cadance's undergarments. The leggings clung tightly to his thighs; as he flexed them, another moan slipped from his throat. Why, in this lingerie, he could have almost sworn that his hips were wider, his rear thicker.

Shining gave his rump a light slap, and couldn't prevent a very unmanly giggle from escaping him as it jiggled lightly. Goodness. He knew he'd fantasized about being a pretty mare...but perhaps he should lay off the second helpings at dinner. He felt his balls throb in his grip, and gave a tender groan. Odd, really, how they felt almost larger than usual. Fuller, even. It was probably just his libido talking.

Liquid arousal ran down the insides of his thighs as Shining traced a single finger around the contours of his package. It filled out Cadance's panties perfectly—more than perfectly, even. Whereas his original erection had stretched them graciously, it now seemed ready to spill over the sides. Shining's eyes widened as he took note of just how long his member looked to be—nearing a foot and a half in length, easily a few inches more than usual—then moaned, a sudden surge of arousal forcing his body to flex in a glowing sense of need.

When his eyes rolled forward again, Shining couldn't keep them from tracking down to the space between his legs. This time, though, there was no doubting that his package had swelled in size. It was actually obscene, now—a solid two feet of stallion meat packed into a dainty little container. At first, he couldn't believe his eyes—and then another surge of pleasure tingled through his veins, sending him doubling over with lust. As he drew himself back up, his chest heaving, Shining decided that he didn't really care.

Without putting either of his hands directly on his stallionhood, Shining began to stroke his erection through the panties, cooing softly as it hardened, lengthened, throbbed. It swelled in his very hands, adding inch after inch with each slide of his soft palms across the damp fabric. His whole body began to sway on pure impulse, his shapely hips and rear bobbing gently from side to side as Shining's soft moans of need filled the air.

And shapely they were—for Shining Armor's stallionhood wasn't the only thing that had begun to grow. His hips flared wide now, looking almost motherly, as his ass pushed out to form a true, bouncy bubble-butt. He grunted to himself, cupping each of his colossal nuts as they pushed past the size of grapefruits, near-overflowing his hands as he struggled to contain them.

Two lumps on his chest began to push out, filling the bra he'd so carefully strapped to his chest. Shining panted, small droplets of sweat forming on his forehead as two small breasts overtook his carefully sculpted pecs—though they didn't remain small for long. As he jerked himself off through the slick silk of Cadance's panties, streams of precum running down the length of his tight-fitting leggings, a lovely pair of C-cups began to push forward from his chest, dropping down to fill Cadance's lacy bra as Shining's eyes squeezed more tightly shut.

He moaned, softly at first, then louder, as each throb of his growing cock brought another jolt of pleasure through his system. It wasn't the only source, though—his rear felt so incredibly sensitive, his flanks so heavy, his chest so...full. Shining groaned, one hand coming up reflexively to begin to massage the now DD-cup breasts hanging low on his chest.

A guttural moan tore its way from his lips as he kneaded the soft breastflesh. His finger brushed against an erect nipple, which was poking hard against the bra even as handfuls of tit began to push past the confines of his bra. Cadance was a well-endowed mare...but even she seemed to have little to compare to the mare that Shining was becoming.

On and on his body swelled. His ass pushed out further, each meaty asscheek filling up further like a pillow, grinding and pressing together as Shining's figure curved out into an image that any model would have been jealous of it. His waist tapered off neatly as his hips grew into a true foalbearing figure, his thighs looking ready to tear his leggings in places. Every part of him was just so thick—and that was doubly true for his stallionhood, which by now had to be a good three foot long, and didn't even look fully hard. His balls, so fat, so juicy, pressed hard against the sides of his legs, squeezable thighflesh depressing beneath the weight of such dense, cum-bloated orbs. His cock was forced to double down against itself, its pre-drooling cockslit pointed directly at the ground as an overloaded Shining massaged both sides of the shaft, no longer able to reach all the way around with one hand.

Oh, and such a mare he'd be. Shining groaned with pleasure, running both hands up his expanding chest as he squeezed a—to his conscious mind, anyway—pair of imaginary breasts. A voluminous pair of pillows greeted his fingers instead, and he moaned cutely as he kneaded his growing bust, both breasts swelling larger by the second, their copious titflesh overflowing his fingers as he groped further.

Perhaps he could wear this ensemble outside—out in the hall, in the streets, even. The forbidden fantasy made Shining's cheeks burn all the more brightly, and he bit his lip, eyes squeezing tightly shut as he moved to grope shamelessly at his massive cock. It was past three feet by now, nearing four, his entire package an absolutely enormous mass that had stretched Cadance's panties beyond any reasonable limit. How the fabric was holding onto those melon-sized nuts, that thigh-thick member, nobody could have known. A steady cascade of precum, cupfuls by the second, ran down steadily onto the carpet as his legs were pushed further and further apart, Shining straddling his own titanic stallionhood with each inch it put on. All the while, the puddle of arousal beneath him grew wider, deeper, muskier.

He pinched one of his nipples, and groaned throatily. Out there...why, everypony would see him. Shining moved to cup one of his enormous breasts and sighed with pleasure as he felt the soft, marshmallow-like flesh sink against his palms. Lost in his reverie, he couldn't help but blush as he pictured all of the stallions eyeing him. All the mares would see him for the slut that he was, even as they grew jealous of his perfect, feminine figure. His hips swayed gently, his fat ass bouncing as if to emphasize the thought. Each cheek had to weigh at least a dozen pounds each by now, and his Cutie Marks were near the size of dinner plates.

The stallions, though... Shining couldn't prevent an effeminate moan from passing his lips as he pictures their lustful, focused stares. Each one would see the bra first—padded, of course—each breast a perky, perfectly round shape. They would drool, pant at the sway of his—her—hips. And all the while, his generous endowment would bob and sway between his luscious thighs, the dark stain on the front of his panties giving away his incredible arousal at his situation.

"Mmff," Shining moaned, his voice muffled as he bit down harder on his lip. Sweat beaded on his forehead, his breasts rippling as he massaged them thoroughly. He thrust one hand into his cleavage and grabbed a heaping handful of titflesh, grunting with exertion as his tits swelled to the size of beach balls. His bust by now reached down nearly to his stomach, and was still growing. Below, Cadance's panties were trembling, the fabric creaking ominously as the flare of his swelling horsecock threatened to brush against the carpet below, the steady leak of precum from his colossal nuts only serving to heighten his arousal further.

Not a single stallion would be able to keep their eyes off his ass. Some might squeeze it—grab it—spank it. Shining moaned, low and throaty, as he imagined another colt taking him—mounting him, even—in the middle of the street. Or perhaps he'd wear his costume to an important meeting, show the diplomats of Saddle Arabia just how much of a girly slut he was. Maybe he'd wear a collar around his neck, and a ring around his oversized cock, whimpering for a chance at orgasm each time Cadance allowed another stallion or mare to leave their hot, fertile load gurgling inside of him.

Each time he pumped his hands around his swollen endowment, Shining felt the weight in front of him redouble. His ass was huge at this point, each tender caress of air against his cheeks sending orgasmic reverberations through every inch of his body. He gave his nuts a hearty squeeze, groaning as he slipped ever-more deeply into fantasy, imagining just how cute, how pretty, how useful a mare he'd make—

With a sudden gasp, he felt his hips buck forward. Shining whinnied, his fat rear twisting as his mighty cock lurched. Four feet of stallionhood stood straight up in the tight confines of his pink-laced panties, jerking forward as volleys of hot spunk erupted from his inches-wide cockslit. Shining moaned, both hands gripping the sides of his shaft as his oversized rump jiggled and bounced behind him, each thrust of his hips forcing his massive asscheeks to slap and bounce against each other.

His cock convulsed like a bucking bronco, each twist or jerk of his hips sending another gallon-sized wad of cum splattering against the space in front of him. His colossal nuts seized up, his fat ballsack pushing his thick, squeezable thighs even further apart as they churned with oncoming seed. Through it all, Shining moaned, a high, girlish squeal of pleasure and delight, his cheeks burning a bright cherry red as his orgasm washed over him with all of the force of an earthquake.

Both knees hit the ground together, only the great padding of his ballsack keeping him from falling any further. Shining’s moans echoed through the room like the howls of a dog, guttural, whimpering groans only made more pronounced by the geyser-like fire of his massive cock. Each lurch of his gigantic endowment, now four and a half feet long and still growing, made his whole body jerk, both exercise ball-sized nuts jiggling beneath him as his larger-still breasts bounced and wobbled before him.

His shaft, caught tightly in the tight fabric of Cadance’s ruined panties, jerked and twisted with each thunderous crash of his orgasm. Shining clutched his breasts in both arms, barely able to even reach halfway around as he rode out the rising tide of climax. Each flex of his member brought another gallon of cum, a wad thicker than his entire head, splattering against the wall, the floor—even the ceiling, the fabric of his pretty pink panties groaning with pressure as his massive endowment convulsed with near-impossible pleasure.

Finally, Shining rode his orgasm out to the end. His body still twitched, flexed, jiggled from the last aftershocks of his pleasure. Panting, he let his head crash forward, his tongue lolling out as tendrils of saliva dripped down his chin.

He came to rest in the greatest, softest pillow he’d ever felt. Shining let himself lie there for a moment, his upper body resting on the enormous, spherical marshmallows before him as his legs and rear weighed upon what felt like a mattress of soft, supple flesh. Thoughts, hazy and lost, drifted through his mind, aimless, purposeless.

One snagged on a corner of his brain, though. What exactly, Shining wondered drowsily, was he lying on, anyway?

His eyes slowly opened. Before him lay twin fields of white. Each mass—vaguely spherical in shape—tapered off at the sides, revealing another white-colored pane, this one shaded with sludgy, oozing textures.

Shining’s eyes widened. His head jerked up—and he nearly found himself slingshotting back when a sudden weight on his chest made the motion all the more difficult. Flushing and gaping, it was then that he noticed that he was still wearing the sleek, pink-laced bra that he’d stolen out of Cadance’s dressers. Somehow, it had managed to stay intact—even when a massive pair of breasts, each the size of a small foal, had grown to fill them.

He prodded one, feeling woozy. They were his breasts. Soft, sensitive, warm. Shining shuddered with a sudden tingle of pleasure, and for a moment, almost thought he could feel something sloshing inside of them.

Speaking of sloshing… Somewhat desperately, Shining was just barely able twist his neck to peer back over his shoulder—only to come face-to-cheek with an enormous, rounded rear that must have been even wider than he was tall. Each asscheek was perfectly shaped, wobbling ever so slightly with the gentle waves of motion remaining from his orgasm. And his Cutie Marks were enormous. A blush tinged his cheeks as he recalled his fantasies. What a mare he was now.

Shining gulped when he saw the gentle contour of a larger, white-shaded orb beneath them. Were those his...balls? He felt one of them throb, and moaned suddenly. Already, he could feel them filling up with fresh seed—even as the dozens of gallons of his last orgasm’s spunk continued to drip down from the ceiling, wall, and mirror that he’d drenched.

Shining’s muzzle quivered, his mind reeling from the sight of himself. He shifted his weight, and could just barely feel the soft, silken fabric of his wife’s panties whispering across his waist-thick shaft. He groped for his breasts, gaping in awe as handfuls of titflesh overflowed his fingers. What in Equestria had done this to him…?

He felt a panic bubbling up in him—albeit one tinged with arousal. He’d thought he’d just been fantasizing; he hadn’t imagined that it had actually been real; and now he had a pair of breasts—breasts! Honest-to-goodness breasts!—that had to weigh nearly a hundred pounds each, and an ass the size of Celestia—

He gulped. He’d fantasized about being feminine, about being noticeable. Well, if he went out like this, he’d certainly be noticed now...

Behind him, the door slammed open. Shining jerked toward it—and immediately stumbled under all of his new mass, going rump-over-head and landing with a heavy thump.

“Aha!” a very familiar, female voice called out. “I knew I’d find who was stealing my lingerie!”

Shining paled. Oh, no. He struggled to get up, but his breasts and ass were just too heavy - and each jerk of his wriggling hips only made his cock harder, his balls swelling up until his feet were no longer even resting on the ground. A moan slipped from his throat, his eyes darting helplessly as he felt his lingerie stretch and groan even more ominously around him.

A smirking, victorious-looking Cadance stepped out from the foyer. Her eyes fell on him a mere instant later.

“...Shining?”