You mean besides the unnatural stretchiness? The usual.

"Huh... haanh~..." Faye quivered and shook, fighting to not collapse on top of Anna, who was near-delirious underneath her as her belly swelled to ridiculous proportions. "I... I... fuuuck~..."

"Indeed you do, Fay-Fay, you fucked her gooood~." Lily sounded positively ecstatic that someone else got to experience her packmate's massive shaft. "I can't wait to see what'll happen to her..."

It wasn't exactly ice water that this sentence dumped on her, but Faye felt her strength return as adrenaline surged through the dog morph. Right, that was a thing with her cum... she'd been so caught up in lust and desire and fucking that she'd completely forgotten to worry about the consequences. Straightening until she stood over the mewling fitness coach, Faye stared down at Anna with a mix of trepidation and excitement. Trepidation because she had irrevocably changed another person's life - again - and excitement because, if she was honest, this power to transform another human being... it felt good.

"Hnnuugh~, it's so much..." Caressing her swollen, pregnant-looking belly almost reverently, Anna struggled to even lift her head. "That was so--hffuuh~!"

Blowing up her cheeks, Anna tensed, her snatch squeezing around Faye's rock-hard rod. The fitness coach's hands flew to two spots just under her sports top, only to migrate along the swell of her belly as her breathing deepened once more.

"Wha-what's g--gh!" Anna arched her back squeezing two spots on her belly as the ones below her top began to darken and bulge outwards into a second set of areolas, with a third presumably forming under Anna's hands. "I-It feels... oough..."

"Welcome to the pack, sweetie!" Lily called over as Anna bit her lower lip and pinched the tiny little nipples that begun to form on her lowest areolas. "I promise you're gonna love it."

"If I can get Faye tuh-to fuck me some more, I--ah! I'm sure I w-wi--iiill~!"

Thinking back to when her tits had been growing in, Faye felt her shaft throb, still locked tight into Anna's pussy. Of course, this meant that none of her cum went anywhere but to where it could contribute to the growth of Anna's new tits. Because even as her new nipples were still lengthening, thickening, her areolas becoming wider by the second, there were now undeniably four small mounds on the front of her body, giving Anna's hands something to squeeze as they roamed over her body.

And Faye's too - the dog morph had decided to enhance her afterglow by helping Anna fondle herself. After all, four hands could cover six tits much better than just two. Also, feeling the proof of her power to enhance others swell under her hands made Faye's heart beat faster and her nipples and shaft throb. Anna hardly minded, of course, gasping and moaning as she and Faye squeezed and caressed her expanding mounds as if to urge on their growth. And grow they did - already they were more than hand-filling, soft titflesh bulging out between Anna's and Faye's fingers as they gently kneaded and teased the sensitive skin.

Little by little, at the same pace as her breasts swelled, Anna's belly shrunk, creating the impression that all that cum went straight to her tits in a perverted version of the old joke of chocolate going straight to one's hips. Not that either of the three had even the faintest idea how Growth-X actually worked. Just that its immediate and less immediate effects where highly enjoyable, if a bit weird.

By now, said immediate effects were so big that Anna's dainty hands had trouble containing them, her original breasts surging bigger along their new sisters and overflowing her sports top. Faye struggled less, being far taller than the fitness coach and thus equipped with bigger hands, but she had more to heft and squeeze now, rolling the middle left nipple between her fingers, eliciting gasps from Anna that were echoed by the dog morph as her packmate's snatch twitched around her length.

"G-god, that's so weird... I'm getting some r-real bazongas here..." Considering that, due to her obviously extensive workout regimen, Anna had not been sporting all that much up top, her speedrunning cup sizes quickly overwhelmed her top. Quickly pulling it down to free her soft, expanding mounds, Anna gasped in lustful astonishment and grinned. "Oooh~, look at those tits!"

All three dog morph's did - after all, Anna's new boobage was almost as large as Lily's, speaking in absolute terms, but on her smaller, more lithe body, they looked massive. And they were still growing. Faye bit her lower lip as she grabbed Anna's lowest pair of tits; by now, they were so big even the biggest dog morph of the three could not hold them completely, her digits sliding over the sweat-slick skin. And those puckered, fat nipples capping them.

"Hnn--uuuh~..." Faye's pointed ears twitched and swiveled towards the door that lead from the main gym to the lobby - because that lustful groan she'd heard had not come from either of the dog morphs.

"The fuck?!" Growing tits, fondling them and cocks lodged in pussies were forgotten immediately as Faye's protective instincts kicked in without any buildup.

Scooping up Anna and pressing her into Faye's breasts, the muscular dog morph stalked over to the entrance with huge strides, barely even feeling the fitness coach's weight or how her breasts kept expanding against Faye's body, and completely ignoring the confused - and muffled - sounds Anna made. The door to the lobby was cracked open, and when Faye ripped it open and almost off the hinges, the receptionist of Phoenix Gym was standing there, hunched over, gaping up at the furious dog morph, cock in hand and the smell of semen rather strong about him. Faye didn't bother to look for the puddle the man had made.