Apple Bloom and her boyfriend show off for each other while growing: her into a big-breasted, bubble-butt wielding goddess(tit and ass growth), and him into a muscular sex god(muscle and cock growth). Then they fuck. Hard.

"Welp," Spike said. He glanced down at the potion in his vial and swilled it around a bit. The purplish liquid lapped against the sides invitingly. "Bottoms up." He upended the vial over his mouth and gulped it down. Out of the corner of his eye, he saw Bloom doing the same.

"Well?" Applebloom asked. "Whatcha think, Spike?"

"I think..." He raised a claw. "Tastes...kinda fruity, actually." He smacked his lips, frowned. "And kinda...urgh!" With a sudden gasp, he felt a shock explode inside of his spine. He doubled over, his arm held tight around his stomach as every part of his body seemed to suddenly explode into flames.

He was breathing hard, sweat running down his body as each muscle tried to twist its way out. Then he felt an incredible tightness around his crotch. His pants, which had only just been baggy, now felt too small, too tight, to contain whatever they were now holding. His claws flew for the waistband, struggled for a moment to untie the knot. His roving claws couldn't help but feel a massive and swelling bulge right between his thighs. Even his thighs, even through the fabric, suddenly felt a lot thicker, a lot harder, than they had before.

With a groan, Spike tore his pants off and let the tightness go free. And not a second too soon, either. With a loud, meaty thwack, something long, hard, and pink tore its way through the edge of his pants and smacked him right across the center of his chest. He stared with wide eyes at the indisputable cock bobbing at the lower end of his vision. It took him a moment to realize that it was his: this thick, veiny manhood.

It must have been a good sixteen inches long! And easily that long around. Spike just groaned again as it throbbed, suddenly soaring up a few inches while his balls dropped even lower between his legs. He could feel them groaning, swelling as they were filled with his seed.

Beside him, Applebloom was going through a similar transformation. Her chest was starting to look incredibly tight, her now thimble-sized nipples pressing up against her shirt so hard that the fabric was basically transparent. She stretched her arms out and moaned as two fist-sized damp spots appeared on her shirt, her breasts swelling from what had been a "small" 14DD (which had never been small in the slightest) to something in the G- or H-range. Soon, her shirt had been stretched so far that it only covered her bust, her midriff bared for all the world to see and her underboob hanging loose just above it.

Her ass, already curved and muscled from years of farmwork, was starting to overflow her tight jeans. Thick rolls of assflesh began to protrude out from the top of her belt. The fabric strained and stretched as each one of Applebloom's asscheeks swelled out into a bubble-butt the likes of which nopony had ever seen before. Spike took one look at that glorious rump and groaned again, that shock exploding inside of him once more.

With a mighty rip, his shirt tore in three places at once: once on each arm, and once down the middle of his chest. He felt a heat, a sense of power growing in his chest. He could see his muscles growing, bulging, his biceps exploding in size and pushing the tatters of his clothing to the floor. His cock only throbbed all the harder as he watched his body grow in size and strength. He'd started at just shy of six feet, but as his chest reached massive proportions and his arms flexed larger than a skinny pony's torso—they had to be twenty-five inches around, easily!—he felt his spine lengthening. Each moment, he could feel his limbs reaching out farther and farther. Six feet became six and a half; in no time at all, he hit (and passed) seven.

Applebloom was growing, too. Not as quickly as Spike, but sure enough, the bottoms of her jeans were inching up over her ankles as quickly as her ass was overflowing it. With another rip, her pants split right down her thighs. Her bubble-butt just leapt out of the back, shoving the fabric down the backs of her legs and rippling proudly for all the world to see. Spike felt something bestial, something needful, grab a hold of him at the sight of that ass, at the sight of her massive, straining boobs, and acted.

He stood up tall and grabbed Applebloom in his thick, bulging arms. She groaned as his pecs, each one the size of a beach ball, rubbed against her growing breasts, Each of her breasts was big enough to hold a good-sized foal now, and both were dripping with milk. Spike's cock, easily three feet long by now and a foot thick, was sandwiched between the growing chests of the two titans. As Applebloom surged up to six foot eight, and Spike to seven foot six, the latter's shaft throbbed mightily and gave off a massive spurt of precum that shot right up to the ceiling and stuck there.

Applebloom groaned in pleasure as Spike's hands roved across her tight ass, her boobs squishing against his chest with every little motion. Her velvety-soft mounds embraced his cock all the tighter as the two of them grew. Spike squeezed his marefriend's rump, hard, and gave his hips a quick jerk upward to drive his cock even further between Bloom's breasts. Soon enough, she found herself exploring his body, too, her slender hands dancing across his thick, veined biceps, her voluptuous thighs rubbing against his tree-trunk quads. Their lips met in the middle, each one exploring the other's body, and another shock exploded inside of them as their tongues made contact. Up and up they surged—eight feet, nine feet—until their heads were scraping up against the ceiling of the kitchen, the floor creaking beneath their weight.

Spike pulled away from the kiss with a deep gasp of air, and winced when he hit his head on the ceiling. He looked over his marefriend, eyed every inch of her incredible body. "Wow," he breathed.

Applebloom planted a kiss on his tip and reached around his upper arm with both hands. They couldn't even reach halfway around. "Damn straight," she said, and leaned in for another kiss.