Gwen has a change, and Roy's having a "Butterfly Effect" moment

Sam turned back to his friend, surprised by his outburst. "Roy, don't do anything foolish!" he shouted over the machine. "The procedure has already begun!"

But before Roy could do anything other than stand there in shock, he felt a strange fuzziness in his head. The edges of his vision went dark, his body felt suddenly heavy, and his breathing became ragged. It took all his effort just to stay standing. He looked up at Sam, a hint of fear in his eyes. "What... what's happening?!" he called out hoarsely.

But Sam didn't notice Roy's struggle. "SCIENCE is happening, my friend!" he shouted dramatically, gesturing back to Gwen's glowing form.

Roy could barely believe what he was seeing. As she glowed, Roy could see her mouth moving, but no sound emitted from her throat. Her face, unlike his, carried no trace of fear, merely a blank expression of mild confusion. Roy never truly saw the changes as they happened. He merely blinked, and when his eyes opened, something on Gwen looked different. He blinked, and she was wearing a red hoody. He blinked, and her skirt turned into a pair of pink cuffed shorts. He blinked, and her hair was shortened considerably into a boyish cut. But most surprisingly of all, was when he blinked, and suddenly her breasts had grown massive, easily filling her new hoody.

And just like that, with a resounding CRACK, it was all over. The hum died, and the machine was quiet once more.

For a moment, the three all stared at one another, each waiting for another to say something first. But the silence wasn't broken by words. A massive pain spiked in Roy's head, his vision filling with stars, and he began to fall forward onto the hard basement floor, drifting into unconsciousness.

The last thing he heard before he hit the ground was Gwen and Sam's worried cries as they rushed to his side.

*

Roy awoke some time later, lying comfortably in a strangely familiar place. He was in a soft bed, lying on top of the comforter, still fully clothed (except for his shoes). His eyes opened groggily to see he was in a room with darkly painted blue walls, most of the space on them covered by posters of men in surprisingly revealing clothing, oftentimes no more than tights. He was confused for only a moment, before he realized what these posters were; they were wrestlers. Posters of muscled grapple men, some wearing truly flamboyant outfits, surrounded him. He turned his head to the side, and realized he was not alone in the room; sitting alongside him was Gwen, looking down at him with concern. Well, the new Gwen. She had the same ears perched on top of her head, and Roy had to imagine she had the same tail tucked behind her. Her hair was the same vibrant golden brunette color, but of course now it was much shorter, giving her countenance a rebellious tomboy charm. Her red hoody did a lot to hide her frame, but Roy could tell she was just as petite as before, her legs and shoulders betraying her gymnast-like physique. But of course the exception to that was her massive chest. The heavy hoody hid their exact size, but Roy had to imagine it was one of the largest pairs he'd ever seen, possibly surpassing an E-cup, not that Roy knew much about bra sizing.

Gwen smiled at him, the look of worry not quite abated, and at this point Roy realized she was holding his hand. "How you doing, buddy?" she asked him timidly, and in a rare circumstance, Roy heard her voice without all the fire and bluster he'd grown accustomed to.

And that was when Roy realized that... he remembered her. He was accustomed to her normal tone. He searched his mind, and remembered coming over to Sam's house for the first time and meeting her as a child. He knew that she never really made any girl friends, preferring to play with the boys (and sometimes get into fights with them). He remembered the times she dragged him into the city to see pro wrestling shows... not real fights, but the choreographed antics of "sports entertainers". He remembered her favorite color (red), her favorite food (grilled steak), and her favorite music (70's and 80's heavy metal). He knew this girl, backwards and forwards, and she was one of his closest friends.

And at the same time, he had those memories from his time without her. The years of being Sam's guinea pig, without the rambunctious antics of an older sister who always seemed to be hanging around them. The strange, almost empty now, memories of a life without this wonderful dog. It felt... strange. Something had happened to him when the machine was used for the second time, that was obvious; but he was certainly thankful in that moment for it. He looked back on those memories, from a timeline without Gwendolyn, and now they seemed, by comparison, empty.

He was broken from his internal struggle by Gwen snapping her fingers in front of his face, her ears twitching in concern. "Hey, are you alright? You're spacing out, dude."

He nodded his head, regretting it immediately, as the headache from before hadn't quite gone away. "Yeah Gwen, I'm fine. Just um... thinking."

They sat there, holding hands for a moment, looking into each other's eyes, before Gwen suddenly realized what they were doing, and shot up out of her chair in surprise. "Good! Good! Alright, I'll uh... I'll get Sam! He needs to, uh, check what's up with you!" She quickly made her way out of the room. Roy couldn't help but notice that he could easily make out the swell of her tits from behind, her small frame doing little to hide her front, but he quickly cleared those thoughts from his mind. He silently chastised himself for being such a horndog. This was one of his best friends. Now was not the time for that.

A short while later, Sam walked into the room, still wearing his lab coat. He was holding a clipboard in one hand, a sheet of paper attached to it, and a ballpoint pen in the other. He walked over to the bed, took a seat in the chair Gwen had used, and regarded Roy solemnly. "Roy, how are you doing?"

Roy chuckled. "I've been better. Please Sam, promise me you're not going to use that machine again."

Sam nodded. "It's been unplugged. At least, for now. But before we deal with that, can you tell me what you experienced?"

Roy filled Sam in on the details; the fuzziness, the darkening vision, the loss of consciousness. "And," he continued, "I can remember being in this timeline now. It's hard to think about, and it's mixed with the memories of the other one, but it's there."

Sam took notes as he spoke, his pen a blur on the page, interspersing Roy's explanation with the occasional uh-huh or I see. "Well Roy, you've lucked out. Based on what I've been able to surmise about the reality rewrite, you were still partially inoculated against the chronotons, thanks to your previous exposure to the quantum shielding." He sighed heavily, obviously distraught by some of the recent events. "It seems, however, that the machine is a failure in its intended purpose. I only programmed a simple hair change, and yet, the process has yielded entirely unexpected results. I should be thankful the only changes to her were physical, I suppose. I don't know if I could handle the guilt if I had somehow erased her personality."

Roy sat up, curious. "Wait, you can remember how she was before?"

Sam nodded again. "Yes, I was well within the quantum shielding bubble during the second test. I can't remember your proposed timeline where she was an animal, but I can say with absolute certainty that she's wasn't always quite so... um..." he stalled, searching for a word.

"Large", Roy supplied.

Sam eyed him suspiciously. "So you noticed too, then."

Roy nodded. "It seems like I've got three timelines worth of memories stuck up in here," he explained. "Guess that explains my headache."