“Doctor!”

Derpy Hooves knocked on the door for the fourth time in thirty seconds. “Doc, you home?” She held her breath—and then let out a sigh when the man failed to appear.

“Hm,” she said, glancing through the little window near the top of the door. It didn’t look like anyone was home. The lights were all out, and not a thing was moving inside.

Her shoulders slumped. “Dang,” she mumbled. She eyed the package in her arms mournfully. She’d planned on delivering it earlier in the morning, but she’d forgotten. Now, with her tummy rumbling and her lunch break just beginning, she was finally free to deliver it.

Except now the Doctor wasn’t home, and she’d waited too long, and it was all her fault. And now she was really hungry because she hadn’t eaten anything for breakfast and she’d been waiting all day to cook that zucchini she’d bought at the market, except now she wasn’t going to get home at all.

Another mailman may have shrugged, dropped the box on the doorstep, and left. But not Derpy. She did her job properly.

“Come on,” she mumbled, prodding at the door knob. “Please?” Biting her lip, Derpy glanced around. Once she’d adjusted the prominent mailman’s cap on her head, she leaned forward and tried the door.

It actually opened. Derpy instantly lit up.

“Yes!” she cheered. Now she’d be able to get home and have lunch! Her grumbling tummy made its displeasure known again, and she hurriedly rushed inside, letting the door swing shut after her.

Derpy held the package to her chest, leaning it against her bust. At only an A-cup, it was a fairly flat surface. She pursed her lips, glancing around the hallway. A half-dozen doors stared back at her.

Now. Where to put it? She had to make sure that it was someplace that the Doctor would find it; she’d be a terrible mailman if it got lost! Derpy frowned, thinking.

She’d been here before, so she knew at least some of the layout of the Doctor’s house. Sure, she was always finding new nooks and crannies and even whole rooms that really shouldn’t have fit in any house, but she knew where the big rooms were. The bedroom, the lab, the—

Her stomach rumbled, this time even louder. Derpy brightened. “Aha!” she said happily. “The kitchen!”

Of course! Everyone loved going to the kitchen—because the kitchen meant food! And right now, there was no part of Derpy’s mind that hadn’t latched onto the image the instant she’d thought of it. If she left the box in there, the Doctor was sure to find it.

She happily made her way down the hall, all but skipping as she neared an end to her errand. She’d done it! She’d found a way to deliver the package, and now she could finally go home and eat.

The kitchen was quiet, the counters cluttered. Derpy found a small nook beside the stove, halfway between a towering pile of pots and a towering pile of dirty dishes, and placed the package down. Then, deciding that it didn’t look quite noticeable, she turned it a bit so that one side was sticking out over the floor.

There. She beamed.

As she turned to go, her sleeve brushed against another pot. Derpy turned, glanced down at it. This pot wasn’t like the others, all metal and rusted and dirty. It was a clay pot, around the height of her fist. Inside, its roots packed tightly beneath a bed of soil, was a flower.

Derpy stared. It wasn’t any ordinary flower. It was bright blue, its petals almost glowing with some strange, otherworldly light. It had two stems, which twisted around one another in a sort of spiral shape. The leaves, instead of being round, were actually square.

It looked weird. It looked bizarre. It looked…

...delicious.

Derpy’s stomach rumbled again, loudly. She glanced over her shoulder to make sure that nobody was there. “Maybe just a little bite,” she told herself, reaching for it. The flower seemed so small beneath her hand, so delicate, so mouth-wateringly fragrant—

When she looked at the pot again, it was empty. Derpy felt something flat and cool on top of her tongue. She chewed, swallowed, groaned. She’d needed that.

It would hold her over until she got home, at least. Slightly guiltily, she peered around the corner, then back at the pot. She hoped the Doctor wouldn’t be mad…

Then again, she reasoned, why leave a flower out in the kitchen if not for eating? Maybe he’d been saving it for dessert sometime; it’d certainly been sweet enough. Something gurgled in her tummy and she burped lightly before breaking out in a giggle.

Still, though, she told herself, she’d have to make it up to him. Maybe bring him a banana nut muffin with his next package. And in the meantime…

She hid the clay pot behind the tower of pans. Her hands on her hips, she eyed her handiwork, nodded in satisfaction, and turned to go. There was a zucchini waiting for her at home, and though the flower had helped, she wasn’t getting any less hungry.

As she made her way down the hall, humming to herself, something odd began to happen. Another person might have said that Derpy’s body actually looked like it was...stretching, getting longer, taller, and fuller as she walked.

Derpy didn’t notice, of course. She was too busy thinking about the lunch that was waiting for her at home. What she did notice, though, was a warm feeling, a tingling that started in her belly and slowly spread throughout her limbs.

The flower that she’d eaten hadn’t exactly been a normal snack. If he’d been there, the Doctor would almost certainly have tried to stop her—mostly because he hadn’t been sure of what, exactly, his little experiment would do. But as the flower she’d eaten went to work, its energy slowly spreading throughout her body, it became perfectly clear what his experiment would do.

Derpy Hooves was a girl of just above average height. Topping out at five feet, seven inches, she and her bouncy personality had sadly never quite been matched by her more feminine assets. At an A-cup, and wearing a uniform that could easily have been worn by a similar-sized male, Derpy had always possessed a flat chest that few women could have hoped to match.

Yet that had already begun to change. Already, by the time she’d left the kitchen, the flower had done a noticeable bit of work. Now a full inch taller than she’d been when she’d started, Derpy and her growth would soon become apparent to anyone who cared to notice. Her breasts, too, were beginning to round out a bit, pushing against her shirt as they filled out nicely.

Another five steps brought her another inch of height. Now five foot nine, Derpy was beginning to feel a bit woozy. As she entered the foyer, she paused and took a deep breath. As her chest inflated, so did the rest of her—she swelled up another inch without any effort at all, her breasts becoming nice and round as they grew along with her.

By the time she’d reached the door, Derpy was nearing six feet in height. Now over four inches taller than when she’d begun, her growing body had pulled the tucked-in coattails of her blouse nearly all the way up, her bigger shoulders lifting them up as she grew. Her bust had passed a B-cup some time ago and was now verging on a C-cup. There was even a noticeable bounce to her chest as she walked, now; if she got any bigger, there was little doubt that most guys would be drawn right to her new assets.

But Derpy, still blissfully ignorant of her swelling size, paid no mind to the sudden tightness of her blouse, or the way her sleeves had begun to ride up on her forearms. She did, however, glance down at her chest to see the most noticeable change.

It was almost as though someone had stuffed a pair of apples down her shirt. Derpy boggled at her new assets, then hesitantly, curiously, gave one a squeeze. That got a soft moan out of her. It felt so soft, so warm, almost like a pillow or a cloud. She gave it another squeeze and this time giggled, amusing herself briefly at the way her fingers sunk into the soft sphere of flesh.

She might have amused herself for longer, but just then, her stomach grumbled again. Oops. She definitely should focus on getting home now—especially she didn’t want to be late at the end of her break!

Humming another, bouncier tune, Derpy trotted outside and closed the door carefully behind her. She was sure, after all, that the Doctor didn’t want just anyone trotting over and letting themselves in.

As she made her way down the front path toward the street, she noticed that she was beginning to feel kind of weird. Her shoes were starting to feel tight, the sides bending outward around her big, growing feet. Her rising shoulders continued to pull her blouse upward, even as her pants rode up over her ankles.

Turning off at the end of the street, Derpy began to tap her fingers against the side of her leg as she hummed. Her longer strides made good time down the road; her longer, more powerful legs were speeding her along. Her thighs, having grown with the rest of her, but somewhat faster than the rest of her legs, were now bulging against her pant legs. No fabric had ripped yet, but it was clear that at some point soon, Derpy’s clothes would reach their limit.

Passing the Ponyville Park, Derpy gave a small wave to the teenagers playing basketball on one of the courts. They stopped their game and stared.

Huh. Derpy could’ve sworn that they used to be taller. What she didn’t know was that, by now, she was already pushing six and a half feet in height, which was easily an inch taller than the tallest player on the court. A big girl, and still growing, it was no surprise that she was starting to attract stares. She wasn’t sure what to think of it, but decided she liked the attention.

But why were they looking at her like that? Derpy suddenly felt a heavier weight on her chest, compounded with a firm tightness, and glanced down. Her breasts had grown right past D-cups, pushing against the fabric of her blouse as they expanded. Her every step as she jogged only pushed her growing body to get even bigger, giving her big, soft tits more energy to grow.

Maybe they were looking at these? Derpy giggled, watching her new tits bounce against her chest as she jogged. She definitely liked looking at them. As she watched, the combination of her new height and her breasts’ new size forced her neckline away from her chest until a full two inches of cleavage were visible on her chest, her now DD-sized breasts forcing the upper half of her shirt into a sort of bowl around their soft, pillowy mass.

She felt the teenager’s stares on her all the way down the street, but Derpy was having too much fun to pay attention to them. Her new assets were much more fun. She giggled as they jiggled in front of her; she cupped them in her hands and played with and squeezed them as she made her way down the street. They were so soft!

An unbidden moan slipped from between her lips as her fingers found a nipple. And they felt so good.

Still fondling her new assets, Derpy continued to make her way home. All the while, that strange energy continued to suffuse her body. She felt good. She felt powerful.

And she was, all the way home, getting bigger.

By the time she’d arrived home, Derpy had added on another three inches of height. Her “girls” continued to grow heavier against her chest, pushing out as the rest of her body grew.

Now nearly six-foot-nine, she ducked without thinking as she went through her front door. She didn’t really need to, but with a doorframe only three inches away from the top of her head, it was a mostly instinctual reaction.

She tucked her front-door key away in her pocket, slightly concerned that it seemed so much smaller than usual. It usually filled her palm, but her hands were anything but petite now. Now, her key was only about half the size of her thumb, and she was almost afraid that she might lose it in her pants.

Given that her pants were about fifteen minutes away from exploding off of her big, growing legs, that might have been a legitimate concern—though probably not the one she was thinking of. Regardless, once she’d gotten over how small the doorknob had felt in the palm of her hand—really, the whole of her house felt claustrophobic now, given that she now stood a full foot taller than she had that morning.

Her moderate discomfort—which was only intensified by the fact that her clothes felt as small as a child’s on her growing body—was easy enough to push aside, though, when her stomach rumbled again. Remembering exactly how hungry she was, Derpy licked her lips and set a course for her kitchen. Though she was anything but “heavy”—the combination of her growing busts and burgeoning hips had started to give her a perfect hourglass figure—the weight of her bigger body still shook the floor with every step she took.

She went straight to the pantry. She was absolutely starving. Derpy had to bend over quite a bit in order to see any of the lower shelves at all. Her swelling breasts, now easily an E-cup, were big and bouncy enough to squish against the bottom of her neck as she bent over. When her stomach growled again, she eyed the zucchini she’d been saving and decided that it wasn’t going to be enough.

Once she’d finished plopping most of her food down on the counter, Derpy scratched her bared midriff—her shirt had lifted up a good seven inches by now, revealing her navel and tapered waist—and eyed the pile of food hungrily. She switched on the stove and got a pan ready for the zucchini—but was more than hungry enough to start snacking in the meantime.

She made her way through most of two bags of chips in what seemed like the blink of an eye, shoving the food hungrily down her throat and moaning quietly in bliss. She hadn’t realized just how hungry she’d been until the first crumbs had touched down in her gut. Eating felt so good...but she was still hungry.

A leftover sandwich, a few dinner rolls, and tomorrow’s breakfast muffins—all of them joined the chips in her belly as fuel for her growth spurts to come. Derpy’s eyes widened, a groan escaping her as she chewed, her body eager to assimilate this new energy input for any future growth.

As she meandered back over to the stove again, her stomach was rumbling once more. She was more than ready to sample her lunch—or, more accurately, to wolf it all down.

Too hungry to season her meal, Derpy just grabbed a serving spoon and scooped half of the pan directly into her mouth. She chewed slowly, savoring the taste. It tasted incredible; she moaned softly as she swallowed.

There was a warmth building in her chest. Derpy rubbed her belly, her eyes fluttering shut as a weird sensation spread through her limbs. Her chest was suddenly feeling incredibly tight.

She stared downward. Her burgeoning breasts were straining madly against her blouse, each one as large as a small watermelon. Any smaller woman would be pulled down by their mass, but at her new height, they were just barely over an H-cup.

Her huge nipples, each as wide as her finger, protruded a good inch and a half through the fabric. Derpy licked her lips; they were so stiff, achingly so. Letting her eyes slowly close, she began to fondle her own breasts, squeezing her nipples and cupping her hands around her new assets. Her hands curved down around her underboob, past her slender waist, and out around her growing hips as she inched past seven feet tall.

Subconsciously, she registered the sound of fabric fibers groaning, popping, tearing as her big body began to push “huge.” Suddenly, with a snap and a ringing twang, the top button of her blouse popped off her shirt. It went flying across the room and rebounded off of the far wall.

Derpy staggered. She caught herself against the wall, her palm spread wide. Her breasts were smushed together, her cleavage spilling out of the gaps between the buttons as it grew bigger and plumper. She groaned as her whole body rumbled, swelling slightly with the promise of growth.

In the blink of an eye, she exploded another six inches taller. Derpy let out a low cry, her whole body shaking as the rest of her buttons popped off as one. The bottom of her shirt had been barely long enough to reach to the top of her stomach; now, it just snapped backward to flutter beneath her armpits, a child’s jacket worn by a big, growing girl.

Now at more than seven and a half feet tall, Derpy was only a foot away from the ceiling. She shifted her weight against the wall, groaning as her well-proportioned thighs rubbed against one another. Bits of thighflesh were already poking out between tears in her pants, and the whole thing looked just about ready to burst.

She surged up past eight feet, and her waistband tore, splitting right down the inseam. She pulled her elbows in toward her chest on reflex; her shirt ripped down the back, separating into two ragged halves.

Derpy’s eyes widened, and she stared down at her bigger body. “I’m...growing?” she said, gaping. A sense of panic was growing in her chest—but that wasn’t the only thing that was getting bigger up there.

Her breasts bounced forward, jiggling madly. Some part of her ached to hold them, to fondle them, to play with them as they and she grew bigger and bigger and bigger—

But she needed to hold herself together. She knew that much, at least. She needed—she needed—

She needed to find a way out of here before she broke through the roof of her house.

She pulled herself upright and tried to stumble out of the kitchen. Unfortunately, she neglected to account for her new size—and, as such, forgot to duck her head beneath the now neck-level doorway.

She banged her chin against the doorframe and let out a yelp. Her hair brushing against the ceiling, Derpy rubbed her jaw, tears coming to her eyes. But she couldn’t stop now. She had to get out of here before she got any bigger.

It was a bit of a struggle to squeeze herself out into the hallway, but she managed it. Her breasts were becoming increasingly unwieldy, now a pair of J-cups that hung down almost to her navel and bounced madly whenever she so much as twitched. Derpy steadied herself against a wall and kept moving toward the front door.

Her body continued growing. Her hips widened out into a childbearing, hourglass figure. Her chest got heavier and heavier, her breasts becoming warmer and softer by the second. Derpy winced as she felt her head scraping against the ceiling; before long, she was forced to lower herself to crawl on the floor on her hands and knees. The hallway—and, in fact, the whole of her house—was fast becoming far too small to contain her growing figure.

She took a long, ragged breath, and winced again as a twitch of her growing, nude—save for a pair of overstretched, groaning panties—butt struck the wall, knocking down a line of pictures. She couldn’t help it. Derpy’s body was just so big, so massive, that damaging the smaller world around her was fast becoming unavoidable.

But she wasn’t done growing—not by a long shot. Derpy was panting now; her pussy, its puffy lips rubbing against her increasingly tight panties, felt like it was on fire. She was incredibly wet down there, and it wasn’t helpful that her tits were getting heavier with every breath, her nipples achingly stiff. She longed to rub them, to caress them, to cup them, to suck—

Not just her clit felt hot. Her whole body felt like it was on fire. She’d continued to grow as she crawled; not, nearly at the exit, she was just as tall on her hands and knees as she would have been standing up at her normal size. A blink of an eye later, and she would have looked down at the Doctor.

Her butt kept pushing out, her hips rubbing against the walls and tearing out deep gouges in the wallpaper as she moved. Derpy grunted as a heat built in her chest. Another growth spurt was coming. She could feel it.

But she was so close now. The front door was mere feet away. Derpy groaned as her clit throbbed, her panties now both damp and ready to burst. Her breasts felt so heavy, her nipples felt so stiff…

...surely just a little touch wouldn’t hurt.

Her hand lifted toward her chest, her fingers twitching in anticipation. The second she closed her palm around her swelling jugs, the titflesh squishing between her fingers, Derpy let out a long, low sigh....

...and exploded in size.

The front of Derpy’s house burst with an explosion of debris, the walls and ceiling going flying in every direction as a giant-sized Derpy grew to fill the space. Passing twenty feet in height in the blink of an eye, she just kept going: thirty feet, thirty-five feet, forty feet.

Derpy moaned, her bigger voice ringing through the neighborhood. Her breasts flopped down onto her chest: two massive pillars, each one hanging to her navel and bulging out past her waist and shoulders. She cradled them in her forearms, oodles of titflesh spilling over her arms as her knees shook and trembled.

Fifty feet. Sixty feet. She was big enough to look down at the top of the neighbor’s house. Seventy feet. She was bigger than the neighbor’s house.

Each one of her colossal boobs was taller than a person; either one of her nipples would have been the length of a normal-sized human’s forearm, and just as wide. Derpy fondled them madly, her gasping breaths heaving her jugs up and down her chest as she continued to grow. Her hips widened with her rear, her round, perky butt settling over the backs of her legs as it got bigger.

Finally, at just under seventy-five feet in height, Derpy’s growth stopped. She groaned happily, cradling her massive bust in her arms. She could just barely reach all the way around, her fingertips playing with her aching nipples as the rest of her body sang with the sensation of size.

Only once she’d stabilized in size did she return to her senses. Derpy took a long, deep breath, a shiver running through her entire body as she looked out over the houses below.

Even the tallest house only came up to just above her nipples, and that one was three stories tall. She blinked, then glanced down at the crowd of people that were gathering beneath her.

“Hello!” she said, waving. The sudden movement of her palm away from her bust set her tits jiggling massively, and a tingle of pleasure surged up Derpy’s spine. A wobbly smile spread across her face, and she groaned for a second, kneading her massive jugs as more and more people collected beneath her massive body.

“H-how’d you get so big?” she heard someone shout. Derpy’s unfocused eyes settled on one of her neighbors in the crowd below: Lyra Heartstrings.

She blinked down at them. “How’d you get so small?” she asked playfully. They really were small. She could probably pick up one in just her hand if she wanted...

“That doesn’t even make sense!” shouted the woman beside Lyra—Bon-Bon, Derpy remembered. “You’re huge! And your house—what did you do to it?”

Derpy glanced down at the wreckage that her house had been. Her big body had long since overgrown it, but she could still make out some debris clustered between her big, nude legs. “Oops,” she said. A nervous grin flickered onto her face.

“Derpy! Oh, Derpy—there you are!”

Derpy blinked again, then found the source of the voice. “Doctor!” she called happily. She reached down for the tall, brown-haired man, her gigantic fingers flexing as they closed around his waist. To his credit, he was one of the few people who didn’t run away screaming as she picked him up and carried him up to her face.

“Derpy!” he said. “I’ve been running all over Ponyville, looking for you! Do you know what you’ve done?”

She at least was sheepish enough to blush. “N-no?” she said, still grinning nervously.

“You ate my experimental subject, didn’t you?” he said.

“...No?” she said helplessly.

“Ingested!” he bellowed. “Swallowed!” At the look in her eyes, he sighed and said—”The flower!”

“Oh!” Derpy brightened. Then she wilted, which still managed to look slightly intimidating, given that she was currently more than ten times the Doctor’s size. “Was I not supposed to?”

The Doctor made a motion to slap his hand to his forehead, and then remembered that both his arms were trapped in Derpy’s fist and thought better of it. “Months of careful research—wasted! And all that for…”

He paused, his gaze bouncing up and down Derpy’s massive body as though seeing her for the first time. “...well, that isn’t to say that there’s a downside to real-world results, but all the same…”

The Doctor cleared his throat and sighed. “Fortunately, I should be able to grow another one from the root culture. And, meanwhile, Princess Twilight is here to try and find a way to get you back to your normal size.” He nodded downward, Derpy following his gaze. A tall, familiar-looking woman with dark purple hair waved up at them. Derpy waved back.

“Unfortunately,” the Doctor said, sighing, “such a cure may take...time. So you may be stuck like this for a bit of time.”

“How much time?”

“A few weeks,” he said glumly. “Month or two, possibly.”

Derpy smiled, then rearranged her arms so that her elbows were resting on the outside of her new bust. “Oh,” she said happily, “I don’t think that’ll be a problem.”