Rainbow Dash is transformed into a living inflable by Twilight to serve as a sex toy for her. And Twilight is cuntinously inflating RD larger while they do it.

“The hay?” Dash yelped. She stared down at her hooves, which squeaked as she rubbed them together. She could fast feel a sensation of immobility spreading through her body as a plastic shine covered her limbs. “What’s - mmff.”

“Just a little spell I found.” Twilight smirked to herself from behind Dash’s field of vision. Dash let out a muffled yelp, but found she couldn’t even turn her head anymore. Instead, her neck made an even more obnoxious squeaking noise every time she even tried.

“Oh, don’t give me that look,” Twilight said as she rounded Rainbow’s side. “I’ll undo it later. We’re just going to have a little fun right now.”

Rainbow’s eyes widened as she noticed something dark and heavy hanging between Twilight’s legs. “Mmff! Mmff!”

Twilight glanced down and giggled to herself. “Oh, yes. That’s another spell I’ve been meaning to try. And new magic is always better together…”

A purplish aura sprung up around Dash’s latex coat and lifted her into the air, her body squeaking all the while. Twilight plopped back onto her haunches, her rigid wings spread wide, as a long, thick stallionhood bobbed up between her legs. An equally large pair of purple testicles were nestled between her thighs, already dotted with small puddles of precum that had dripped from the tip of Twilight’s shaft.

Rainbow Dash squeaked again as Twilight’s member poked up against her latex pussy lips, Twilight’s lubricated head slowly rubbing against Dash’s inflated thighs. “Oh, don’t worry,” Twilight said with a sultry grin. “This won’t hurt. You’re a toy for me now, so in a way, you’re just doing exactly what you’re meant to do.

“But you might be,” Twilight grunted, suddenly screwing up her eyes as the head popped in with a loud schlick, “a bit - ack - tight!”

A purplish aura sprang up around her horn again as Dash’s latex pussy slowly pressed down against Twilight’s monstrous shaft. “But don’t worry,” Twilight went on, panting a bit. “We can - fix that!”

A strange, electric tingle ran through Rainbow Dash’s body - and then immediately, she started to feel incredibly, horribly full. She felt bloated, like she’d just eaten ten pies, scarfed a whole cake, and quaffed an entire barrel of cider to wash it down.

And, when she glanced down, her body seemed to resemble that sensation quite well. Her belly had swelled outward until it resembled a rounded balloon hanging below her chest. One look to either side, though, proved that her limbs had swollen up as well, stretching farther to either side of her - and rounding and bloating out quite generously, too.

“Mmff,” she grunted a final time, as her plastic pussy expanded with the rest of her, her marehood’s lips dripping a steady stream of alicorn precum even as more room cleared out inside of her.

“Ah,” Twilight said, moaning as her stallionhood finally pierced all the way through into Dash’s inflated marehood. “Now that’s much better.”