Sweetie Belle: Macro/Excessive cum/Excessive arousal/Futa (After a botched spell and a potion brewed by Apple Bloom, an excessively aroused Sweetie Belle heads toward Manehattan to find her big sister, but along the way, another thought slowly begins to replace her original intentions with a more...fun one, for her at least.)

Sweetie groaned as her back rubbed up against the ceiling of the Boutique? “Apple Bloom?” she said. Her back arched, her butt thrust out and broke through the wall. Her cock emerged from its sheath and flopped against the side of her leg.

She groaned again, louder, as the roof began to crack and splinter. She’d been just under four feet an hour ago. And now, she must have been over three times that size, and growing all the time. A pair of enormous nuts, each one as big as she’d been before, dangled below her gaping and growing marehood.

Sweetie gasped as the roof, with a final ear-splitting groan, shattered around her growing body. She blinked rapidly as her growth spurt took her through the very top of the Boutique. Twenty feet became twenty-five, and by the time she hit thirty, she was staring down at the wreckage of the Boutique around her hooves.

“O-oh,” she said. Ponies were starting to gather around her, whispering, pointing. She glanced over her shoulder and bit her lip. “Apple Bloom?” She had to be okay. She’d just…left or something. That was it.

“I’m going to go find Rarity,” she said. “She’ll fix this.” Then she turned and walked down the street. Ponies had to cluster to the sides of the road, so wide was Sweetie Belle’s stride. Her monstrous cock, now eight feet long and still growing, swayed from side to side. More than one pony had to duck to avoid being caught in a glancing blow from the filly’s flared head.

It wasn’t long before Sweetie came to the Ponyville train station. On the course of her walk, she’d nearly doubled in size, reaching an impressive sixty feet in height. Her flaccid shaft hung down past her knees, and each of her cum-filled orbs could have easily held a full-grown pony or three.

She frowned down at the tiny little train in the station. Ponies all around it were staring at her, blanching, but she didn’t pay them any mind. There was no way she’d make it to Manehatten in that tiny thing. But how else was she to make it to Manehatten to find Rarity?

She glanced up at the horizon. An old oak tree blew gently in the warm summer breeze - and, she noticed, just barely came up to her chest. A grin spread across Sweetie Belle’s face. Maybe walking to Manehatten seemed impossible to a filly…but to a giant, it seemed a lot more doable.

So she set out, her long and growing legs making lengthy strides across the countryside. Before she left the Ponyville city limits entirely, an image sprang into her mind, unbidden: the Friendship Express, its cars wrapped tightly around her throbbing cock. Maybe she couldn’t ride it to the city, but she could certainly ride it another way…

Biting her lip, she pushed the image away and continued on. But the damage was done. Her shaft was already beginning to lengthen, her balls beginning to swell with seed and arousal.

As she walked further and further, she grew larger and larger. And as she grew, each step became longer, her stride became faster, and her confidence got stronger. The hundred-foot milestone passed soon enough, and by the time she hit one hundred and fifty, her lower lip was starting to twitch with arousal. Her stallionhood, by now, was nearly fully erect, reaching a good seventy feet from her crotch to the bottom of her chest.

It slapped wetly against her stomach, now drooling a small river of precum behind her. Her nostrils flared, taking in the scent of her own, nearly overpowering musk. Yet somehow, Sweetie resisted the urge of her own arousal. At two hundred feet, she began to see a glimmer in the distance - Manehatten!

She soon picked up her hoof, leaving a gaping crater in the field beneath her, and set it back down on the main road into the city. The asphalt cracked beneath her enormous weight, the entire street groaning as she moved herself fully into the outskirts of the city.

Rarity was here somewhere… But a chance image out of the corner of her eye nullified that line of thought quickly.

It was herself - or, more accurately, her reflection, illuminated in the glass of a skyscraper. Sweetie Belle eyed her reflection approvingly. She loved the way she towered above the city, loved the way that the skyscraper just barely inched over her. She loved the way her massive cock, now fully engorged, swayed between her legs. She took a deep, long sniff of her own musky scent, her lungs filling with promises of sex.

Sweetie plopped back onto her haunches in the middle of the street. A smaller building caved in beneath her massive flank, but she paid it no heed. She had bigger things to concern herself with. Slowly, biting her lip, she began to stroke her massive, muzzle-reaching erection.

Gods, but it felt good. Her hooves slid up and down her length, which was soon lubricated by the dripping river of pre from her tip. Her balls throbbed and churned, swelled and sloshed, pushing her legs apart as they filled with more of her seed. She grunted, groaned, working her shaft harder than ever before. She opened her muzzle and gave it a tentative lick, shivering all over as an electric tingle ran up her spine.

She was so big, she realized. Bigger than anypony. But not big enough. As she masturbated, she began to grow again. Her cock seemed to grow faster than her; by the time she hit three hundred feet, it towered above her head. Its weight was soon so great that it pushed her onto her back, demolishing another block of buildings as her sloshing balls spilled over her legs.

Pump. Pump. Pump. Sweetie squeezed her eyes shut, stroking harder and harder and harder -

- and then her hips were jerking, and she was gasping, moaning, as the orgasm washed over her. A flood of creamy white spooge erupted from her tip, waves and waves of giant filly cum washing over the city again and again. She moaned even louder, thrashing from side to side as the pleasure threatened to overwhelm her. She was growing again, creeping past five hundred toward six hundred, seven hundred. Her cock was still erupting, blasting out rivers of cum, ropes of spooge the length of city blocks, drenching the entirety of Manehatten in a thick blanket of white -

Somewhere uptown, Rarity felt the ground shake beneath her hooves. She put down the dress she’d been working on, glanced out the window, and paled.

A massive white stain had covered it, and was slowly dripping down the side of the building. Her cheeks colored. “Oh, my.”