As they fucked, Jeff noticed a change in Jenny first. Her eyes were closed and she was moaning as she thrust her own hips at Jeff's crotch, trying to match his rhythm. Through it all, Jeff heard her voice begin to change. What had started out as the high-pitched gasps and squeaks he was used to had now dropped to a deeper, more mature sound. As he stared at her, he saw that her face was changing to match these new sounds. Where she had once looked like a teenage girl, Jenny's features now aged into her 20s, and then 30s. Before long Jeff would have sworn she was a 40 year old woman based on her face alone.
Jeff looked down her body and was actually able to see her young, smooth breasts expand. They grew from B to C to D cups. And still, they weren't stopping. Jenny felt the weight on her chest and looked down at her body. She tried to speak but the pleasure from Jeff's cock made it difficult.
"Wha... what... what is happening... to... mee!" she managed to cry out.
"You don't know!?" yelled Jeff, alarmed.
Jenny's head continued to bounce up and down on the pillow as she was fucked. "I do, I mean, I set it to... Jeff! Look at you!"
Jeff looked down at himself. His body was expanding, but he wasn't getting fatter. He was simply growing... up? His chest changed from a scrawny teen's to that of a well-conditioned adult male. He was also pretty sure he was growing taller. Looking down at his arms he saw his skin start to tan and then get even darker. Dark hair sprouted from his chest and arms. He was changing into a completely different person.
He looked back at Jenny and saw her head finally slide all the way off of her pillow. She couldn't have been much more than 5 feet tall now. "Jenny!" he yelled. "You're shrinking!"
"No," said Jenny. "I mean, yes but not much. I'm just getting shorter." Sure enough, his girlfriend was actually getting bigger overall. Although her head and body were sinking down the bed, her stomach was growing rapidly, not to mention her breasts which were now clearly four times the weight they had started at. Jenny squeezed her massive breasts and moaned, her small hands barely making a dent in the massive fleshy balloons. Jeff felt himself rise off the bed as Jenny's butt grew, lifting them both up.
The experience of fucking the massively large woman beneath him was totally different than when he had started, but Jeff decided they were both amazing, just in different ways. He grabbed one of her breasts and squeezed, his now-larger hand still looking tiny in comparison to the globe it was holding. "God, Jenny. You're... you're..."
"I'm huge!" she cried out, more shocked than upset. Running her hands up and down her hips, Jenny realized that the sensations coming from her crotch were distinctively better than when they'd started. The sex drive of this body was clearly better tuned than hers ever was. She felt herself orgasm but bit her lip and stayed quiet. This was the third one so far and she was having fun downplaying them so Jeff would keep working at full speed.
Jeff looked down their bodies and watched as his cock kept thrusting into her. Her thighs were expanding, making less space for him to occupy, but still he kept at it. He saw the area around her vulva begin to darken and the color spread down her legs and up her body. She was getting darker, but in a different way that Jeff had. He watched her hair darken and her cheeks and lips puff up.
"Jenny..." She looked up at him with all new eyes. "Jenny, you made yourself Latina."
She looked at her body. "A fat Latina." She shook her belly and watched it ripple and jiggle. "I must weight 300 pounds!" she said in awe.
"And you're like 50 years old" said Jeff. Jenny touched her face and felt the creases and lines there. Her mouth was open with shock. Jeff must have been nearly six and a half feet tall. Jenny was sure she was under five feet now. It was a struggle for them to even kiss as her head was basically in front of his chest now. She admired the thick black hair there and began to play with it. She had started fucking a teenage boy but was now enthralled by the full fledged MAN that was currently riding her. She raised her legs straight up to let his now-massive cock sink as deeply into her as possible.
She watched as Jeff's totally new body continued to fuck her, making every roll of fat on her body jump back and forth repeatedly. It felt like she was watching a porno, neither of the people she could see looked familiar. She finally looked up at Jeff. "You look like a weightlifter! From, like, India or something."
Jeff barely heard her. He was hypnotized by Jenny's swaying boobs. His eyes locked on her dark nipples, he felt a strength in him like never before. He lifted himself on his arms and felt the oddness of watching two strangers have sex right in front of him. "Jenny, I..." but he couldn't finish his thought before his balls clenched, his cock jerked, and he emptied himself into Jenny's warm pussy. Jenny moaned as she felt yet one more orgasm wash over her. She watched this large man shake and moan as he pressed his hips against hers and held them there. She felt everything get warmer and wetter inside her vagina. She wrapped her legs around Jeff's strong thighs and reveled in they feeling of draining a man dry. Her hips vibrated as she instinctively tried to coax every last drop out of him.
"Oh my god," she gasped. "That was so incredible. So, I set the machine to make us random people, Jeff. I thought we'd be like us but older or something. I didn't know it would make us complete strangers! This is so weird! You're so big! And so am I, but you know, in a different way. Oh my god. And I'm a total MILF and you look like you're 25. What the heck, I'm like a horny old lady or something!"
Jeff could do little more than breathe heavily as he lowered his body onto Jenny's large frame. She felt like a warm mattress to him and he welcomed it. They were both silent and still as they felt the totally strange feeling their new bodies were sending them.
