Vinyl Scratch hyper ass inflation.

“We ready to go?”

“Oh, you betcha,” Neon Lights said. He was slurring, Vinyl noted, but she didn’t really care because she was slurring too.

“You ready to go down?” she asked, chuckling. “On this?”

She planted her hooves on the side of the bed and waggled her flank up in the air. She knew he wouldn’t be able to keep his hooves off it.

“Oh, baby.” Neon grinned as he made for Vinyl’s ass and squeezed. “I’ve been waiting all night for this.” His stallionhood was already sprouting from beneath his legs, already at half-mast and showing no signs of stopping. “You got that spell ready?”

“Maybe. What if I think my butt’s big enough as is?”

He gave her rump a smack and smirked. “Scratch, I know you better than that. No ass will ever be big enough for you.”

A light blue aura sprang up around Vinyl’s horn, and she smirked right back. “Is that right? Well, let’s find out!”

Neon swayed slightly with a stupid grin on his face as his hooves roamed over ever inch of Vinyl’s ass. As far as flanks went, it was already pretty well-sized; long worknights with only junk food to eat didn’t do much to keep a mare’s figure slender. But he’d always liked that about her.

“More cushion for the pushin’,” he slurred. Vinyl grinned slyly and bumped her rear up against his crotch, making sure to give his growing cock the barest of squeezes as her ass started to grow.

“And there’ll be plenty of pushin’,” she said.

Already, her rump had swelled up to the point where it was obviously larger than before. Neon looked like a foal in a candy store as he squeezed, pinched, and humped her growing ass.

Soon enough, though, it was almost overflowing his hooves. Neon looked ecstatic. Vinyl just looked horny as hell.

“I’ll bet,” she huffed, as Neon hotdogged her with every ounce of determination his drunken mind could summon up, “that there ain’t a bigger ass in all of Equestria.”

“You think you’re the biggest?” Neon asked. He hugged her assflesh to himself as he felt his dick slide through her cheeks. His balls slapped against her growing rump, his pre providing easy lubrication for each thrust. He gloried in the sensation of her flanks filling his grasp, in the sight of her cutie marks swelling until they were over half the size of his entire head.

Vinyl grinned at him, her giant ass wobbling profusely. “Babe. I know so.”