A nerdy tigress invents a device to steal her boyfriend's muscular build. Explicit.

The last time Sam had tried to spice up things in bed, she'd nearly given her boyfriend an electric shock.

She was a tinkerer by nature. She was never happy when something just worked. She had to know how it worked, why it worked, if it could do its job faster, and how many volts she could run through it before it started smoking. The inner workings of a device spoke more to her than most people did. She didn't get out a whole lot.

Somehow she'd found a boyfriend in Ivan. Actually, she knew exactly how: physics tutoring. Ivan needed it for his distribution requirements, and she wanted a chance to sit and stare at the cute hockey player while he tried to stomp his way around unit conversions.

They couldn't have looked more different. Maybe that was why Sam wanted to make it up to him by coming up with new ways to have sex: because she didn't feel like she was enough for him on her own. She was five foot four at her best, a tigress with stripes that almost looked like glasses and a soft midsection that spilled out a bit if she wore anything too close-fitting. Ivan was six foot five, broad chest, with the sort of shaggy handsomeness that arctic wolves were ideal for. She spent her time in her workroom messing around with disassembled microwaves and scrapped lab equipment, while he was out at the gym, keeping himself in shape.

And he still loved her, which was why she wanted to do something great for him. Since he was out of town visiting his parents for the weekend, she had some time to figure out what to do.

Sam sat down at Ivan's computer with a photo of his face taped around her head. The computer popped on, displaying a feed from the camera. She held still while it looked for his face, found it, checked it, and then opened up his account.

He'd told her that she was the perfect girl for him already, but she was smart enough that she didn't believe it. It was nice of him to say that, though.

Sam opened his internet history and filtered it. Anything that seemed like porn, anything that'd say what his secret favorite thing was that she could do for him. By process of elimination, she knew that it wasn't going to be pegging or shock collars.

Sam didn't need more than a minute to find his porn, and when she did, she felt vindicated. Ivan did want to get a bit dominated. That much she'd worked out on her own. She wouldn't have guessed quite how he wanted it, but she figured it was doable. She just needed time and the right materials.


With one bag of parts from the electronics store and one bag of pilfered junk from the scrap bin behind the campus biotech facility, Sam climbed into the elevator. She dropped the bags and checked the time. Only ten thirty, and it was still Saturday. Plenty of time before Ivan got back on Monday.

"Hey, can you hold the door?" someone called across the lobby. Sam flinched. Getting brought out of her own thoughts scrambled her brain. She pressed a button at random, and got Door Close instead. As soon as she realized, she zipped her finger over to the Door Open button. The doors were an inch from closing, but they pulled back.

Sam buried a polite but embarrassed smile beneath her fur. Standing outside were her downstairs neighbors whose names she couldn't remember. There was the butch hyena girl with a natural mohawk (she knew tai kwon do), who stood a full head above her shaggy-haired, effeminate boyfriend, a jaguar (he did yoga). The only reason Sam knew anything about them was that they went to the same gym as Ivan, so he'd mentioned them in conversation.

"Thanks," the jaguar said.

"You too. I mean, you're welcome," Sam said. The hyena chuckled warmly and put an arm around her boyfriend. The silence that ensued while the elevator rose made Sam's cheeks burn.

"See you, Sam," the hyena said, pulling the jaguar along as they got out one floor below Sam's.

All Sam could manage was, "Yeah," as the doors closed.

She took a few deep breaths. The weight was lifted off her chest. She was alone again. Obligatory small talk was the worst. In a minute, though, she was carrying the bags into her apartment, putting the whole ordeal behind her. No time to worry about social graces when there was something to be built.


Monday afternoon dragged by at a rate of hours per minute. Sam sat in the bedroom, trying to occupy herself with her computer, and trying not to pay too much attention to the black box sitting on the desk nearby. She'd enclosed all the parts in a generic plastic case, featureless except for the holes she'd drilled for the power cable and the red switch on top.

After the eternity of 2:37 PM, she heard the front door opening. Her ears perked up and her tail swished through the air. A few footsteps, and then they stopped.

"Sam? Why is my face in the trash?" Ivan called out.

Sam came out, leaning against the bedroom door. Ivan was holding the printed-out mask of his face. He had on a tank top and shorts and looked amazing as usual. His fur stuck out over his clothes in a few places, shaggy enough to make him look even larger.

"Don't worry about it," Sam said. "Come in here! I want to show you something."

She slipped into the bedroom. Ivan came in a moment later, shifting the weight of his bag off his shoulder and dropping it on the floor.

Ivan spotted the box as he came in. He pursed his lips. "Sam, if that thing's gonna shock me…" he began.

Sam butted in, the way she always did when she was excited to show something off. "No, this is way better!" She flipped the switch. The electronics inside the box crackled. She could smell ozone in the air.

That was the easy part done, now for the hard part. She stepped forward, looking up at Ivan. She leaned up on the tips of her paws, set a hand on his chest, and pulled his head down to kiss him. All the eagerness in her body, and she still couldn't just say she wanted to have sex.

One of the many ways she was lucky was that Ivan had learned how to tell when she wanted something. He put his hands on her hips and guided her toward the bed. Ivan leaned out of the kiss and grabbed the hem of his tank top. "That thing's definitely not going to shock us, right?" he asked.

"Definitely," Sam said. She giggled, but it was more excited than mischievous. Already, she could feel little throbs and aches running down through her arms and dancing around her thighs, concentrated in areas of muscle mass.

Ivan dropped his clothes onto the floor beside the bed and rolled onto the mattress. He was a rippling, shaggy, white pillow waiting there for her to climb on. Sam shed her pajama pants and her old tee shirt and crawled up onto bed next to him, then straddled him.

An 'nng' rolled out of the back of Ivan's throat. Sam felt what she thought he was probably feeling. It was prickly, like static electricity, but inside her body, underneath her skin. Her striped fur bristled. Her thighs tightened around his waist.

"It's been a while," she said, wiggling her ass like a cat getting ready to pounce. Then she lay forward on his chest, leaning up all the way to reach his face and give him another kiss.

Her mind wasn't on the kiss, though; she was thinking about the two factors that increased rate of transmission: distance, and contact surface area. There wasn't much she could do to increase either of them now, except for the obvious…

"Come on," Sam whispered. She bumped her hips against Ivan's waist. The prickling static eased off, but didn't disappear. Instead, it became more of a slow flow, a current running in a circuit from his body into hers and back.

Sam experimentally flexed her arms and shoulders. The difference now was barely visible, but she felt different. How much of that was placebo? She couldn't say, but she didn't feel as much like a rag doll as usual. As Ivan gently pushed her around, getting the two of them positioned, she felt like she could push back if she tried.

Sam clung to Ivan's chest with both arms and let out a faint growl. He chuckled down at her. "Feeling possessive, huh?"

Sam's ears grew red and warm, and she didn't say anything, but she would have said yes if she wasn't too bashful to say it.

One hand on her ass, Ivan lifted Sam. Her tail flicked eagerly through the air. And then, Ivan pressed inside her, spreading her open, making her eyelids flutter. Whether it was the sudden penetration or the induction field the device made, Sam's whole body felt electric.

She shoved herself up against his chest, tight enough that her short tiger fur mixed with his long arctic wolf fur and blended together into a warm blanket between their bodies. She felt each beat of his heart against her chest, and imagined that each beat was driving his blood into her body.

The current running through her muscles made her whole body buzz. It felt like the gentle vibration of a machine whirring away, building up a glowing heat as the current did its work. Sam tightened her arms. Her fur bulged slightly. She tensed her back, and felt the tightness across her sides. She clenched her stomach. Her soft belly sucked in when she flexed her abs.

A low groan left her throat as Ivan rolled his hips beneath her. He pushed in and out, easy and lazy for now, just enjoying being back in bed with his girlfriend again.

"Have you been working out?" Ivan asked. The change to his body was imperceptible so far. He brushed his hands up and down along Sam's back, gently rubbing her tighter, slightly thicker muscles.

"Sorta," Sam said, working to keep herself from grinning.

Sam hadn't been sure if she'd like doing this at first, but now, the more she got into it, the better the idea sounded. She wanted to take more of the creeping, electric power into her own body. She watched Ivan's biceps closely. They bulged just a bit less; not even an inch of diameter lost, but it was something.

Her core tensed, from her chest to her lower abdominal muscles. Sam clenched down around Ivan gently, holding him steady for a moment.

"Maybe you can take me to the gym some time," she said.

"Sure," Ivan growled. A hand on her hip, he pushed past her tightened muscles, continuing his slow rhythm, raising her into the air and bringing her down with each full motion.

Sam's shoulders popped quietly. The joints had to adjust to the new bundles of muscle they were connected to, her thickened shoulders and the low, corded swell of her upper arms. Her hips cracked when she tightened her grip on Ivan's hips. Her thighs flexed, squeezing her boyfriend's sides.

She curled her back, leaning up until a few of her vertebrae let out soft pops. An extra two inches of height, she estimated, given how her eye level now reached up to his collarbone instead of his pecs.

Sam lay down flat against Ivan's chest, her cheek on one of his pectorals, ear pressed against his fur. His heart beat faster than before. She pushed down, squeezing their bodies together again, imagining that she could encourage the flow along by pushing on him, like she could squeeze his mass right out of him.

Her stomach had flattened out and her love handles had rolled back into her body. Sam didn't look like someone else; she still had her own figure. She was just lighter around the middle. She felt like she could fly, though, or like she could do a backflip, or stand on her hands for a whole minute.

"More," she said through clenched teeth. Ivan held onto her lower back as he picked up the pace. She could have said she was hungry for more, but the feeling she had was the opposite of hunger. The more she took from him, the more she wanted. She could probably run a whole jog without being winded, or pump her way through an entire aerobics class with nothing more than an easy sweat.

That wasn't enough, though. He hadn't even noticed yet.

Sam reached beneath Ivan, clutching at the bedsheets. She balled her hands into fists, holding onto the top sheet, elbows bent, straining her whole arm to hold on. She sunk her footclaws into the sheets too, flexing her thighs and her calves. If she tightened her body like this, maybe it would speed up the process. At the very least, it would work through the fifty-kilojoule heat that was buzzing through her growing body.

Ivan's pecs were steadily losing mass, and Sam needed to curl over more to keep her head on them. So instead, now she leaned up to press her lips to Ivan's again. She pushed down into the kiss, not trying to impress him in any way, but when she leaned back, he had a surprised look in his eyes.

"Wow, eager?" he said, panting softly. Usually, he didn't have to work quite so hard to keep up the pace.

"You could say that," Sam said, licking her lips, grinning.

Sam sunk back down against Ivan, wrapping her arms underneath his armpits and hugging him close to her chest. She had expected the feeling of strength and power, but what she hadn't anticipated was simply the feeling of having more mass. Her arms didn't fit as closely against Ivan's body, since there was another extra inch of muscle padding them out. Even if she held her arm against her side, it felt like it was being gently pushed away from her. It wasn't a bad feeling, but it made her feel even bigger than she was.

Sam felt like she could get into rock climbing, or kick boxing, or, hell, even football. Sports made more sense now that she was stronger herself; you wanted to get a chance to use all that brawn, right? She could probably even hold her own doing some bench presses.

Clutched tight to Ivan, she felt as he began to groan and his shaft began to throb. 'So soon?' she thought.

"Sam! What's—what's going on?"

Ahh, that was why. He was figuring it out.

Sam shifted, looming over Ivan, putting one hand down beside his head. He got to look up at her, past the taut muscle of her forearm and her gently bulging bicep, up at her big, confident smile.

"I know what you like," she said.

"What!?" Ivan yelped. He gulped dryly. He held onto her back, trying to keep himself steady, but his body was taking over.

"You want me to get strong," she said, rubbing with her other hand at the tuft of fur on his chest, feeling the dwindling but still tightly-packed pecs beneath. "And I'm gonna make you watch."

"Sam, I—nngh, ohh…" Ivan sputtered, before his head rolled back and his hips flexed up and his load burst out in thick, quick blasts. He was left panting and gasping for air, used to a stronger body, used to having more strength and stamina.

"You're not getting out of this just because you finished," Sam growled, clenching around Ivan to keep him from pulling away.

"I gotta recover," Ivan panted. His tongue lolled out.

"Too bad."

While Ivan was winded, Sam hadn't broken a sweat. They were both about the same size by now, though Ivan was still a bit taller than Sam was. When it came down to muscle mass, though, they were evenly matched. They looked like a perfect pair now; a strong tiger and a strong wolf, going at it. But Sam didn't get up to switch off the machine. She didn't even give Ivan a break, no matter how much he panted and whined about needing a minute.

"It's me time now," Sam said as she leaned back from Ivan's chest. No longer pushed tightly against him, she sat up, kneeling over him, legs still straddling his hips. She dragged her claws back through her hair, tossing it back behind her. Another hand worked its way up her front until it reached her chest. She wrapped her fingers around one of her breasts, squeezing it, showing off to Ivan.

"Look, you're giving me tits too!" she said.

Ivan's broad, barrel-chested build shrunk slowly, sliding down toward more unremarkable proportions. At the same time, Sam's chest, which had never been flat but was also never much to look at, was blossoming with new mass. While her pecs slowly puffed up behind her breasts, her breasts themselves swelled out heavier, rounder, softer: the sort of breasts that'd look great squeezed into a sports bra.

"Sam, turn it off!" Ivan said, wriggling underneath her. Thanks to the slow grind of her hips, he was starting to get hard again. If he'd told her to turn if off like that, all anxious, at the beginning, she might have done it. But now, she was riding a wave of confidence, one that was surging up bigger and bigger underneath her the harder she pushed against Ivan.

"No," she growled, "My muscles now." She lifted her arms up and flexed for him, just to show off. She wasn't going to let a little struggle stop her.

With each roll of her hips, her abs rippled down her stomach. There wasn't a hint of extra weight left, just smooth fur covering a tight washboard. Her ass flexed as she rolled forward. She grabbed Ivan's hands and shoved them onto her hips, holding her ass. Ivan, all big and buff, had a hell of a cute ass, and now she was getting all of it. The muscle swelled with each push, matching the pace at which Ivan was shrinking beneath her. Her ass was heavier, rounder, all tight glutes and tasty curves. She'd look perfect when slipped into a pair of track shorts.

Sam rolled her back again. More vertebrae made soft pops and creaks. She was growing steadily taller, giving her muscles more room to grow. She had to be over six feet tall now. Everything looked further away, from Ivan to the bed to the machine, whirring away on the desk.

As Sam dropped down over Ivan, a rumbling rose up in her stomach, climbing up to her throat, peeling back her lips and escaping in a sharp, savage growl. She felt Ivan wiggle underneath her and his cock throb.

"You want that?" she asked, grinning. Were her fangs bigger now, or did he just look more intimidated by her? "You want a girlfriend who roars when she fucks you?"

Ivan tripped over his own tongue, but managed to nod quickly. Sam grinned. She was outclassing Ivan now; she was in the driver's seat, the bigger one who could take control. He was still strong, sure, but he was more and more lithe the longer she kept him there.

Sam's tail lashed wildly behind her while she picked up the pace. Each thrust drove Ivan into the bed, and together they bounced, with the sound of creaking springs beneath them. Maybe the hyena and jaguar downstairs could hear them. If they did, then Sam didn't care.

She wasn't even trying to play it up for Ivan any more. Somewhere not long ago, it had crossed the line from doing something fun for her boyfriend, to doing something fun for herself that he'd enjoy too.

"Come on, you call this strong?" Sam growled. She flexed a bicep that was too big for her to fit her hand around. "I know you do bench presses. Let me see some beef!"

At first, Sam didn't know why Ivan's cheeks turned red, but after a moment, she realized she'd never seen him embarrassed before. Somehow, that only encouraged her even more. She started coming down so hard that the two of them bounced up into the air. She could only keep that up for a few thrusts, but it was fun to toss him up, watch him twist in midair, then land back down on the bed with her on top of him.

"Someone feeling shy? Don't worry, your girlfriend's here," Sam said. Though he whimpered shyly, she could feel his excited throb inside of her.

Sam tossed her head back again, twisting her hair back into a ponytail. Her shoulders spread wide as she reached back, and her breasts rolled to either side, opening up her cleavage to the light. It was all pale, creamy fur in there, nestled between the black and orange of her fur. Her breasts were like thick, heavy balls each, bouncing, jiggling as she moved.

His broad chest had been enough to push her a size or two above double-D cups, and the taut muscles beneath them helped accentuate their size. Sam clapped a hand around one breast, squeezing the nipple between her two fingers. She let it pop free, then rolled it between her finger and thumb.

"Thanks for these tits, they're great." Sam licked her lips, then bent forward, falling down against Ivan. Her chest fell against his head, his chin poking into her cleavage. "Suck my tits," the strong tigress purred, still holding onto her nipple. While Ivan stared up at her awe-struck, she scowled and snarled, "Suck it, shrimp!"

He looked startled and opened his mouth, closing his lips around her areola. He lapped and sucked, and as he did, her skin grew stiff and swelled up until her nipple was firm and tender. Then she popped it out of his mouth, and shoved the other nipple in front of him.

"Y'know, if you can reach my chest like this," she said while he sucked, "I'm taller than you." He was barely six feet tall any more, and she was at least six foot six of rippling tigress.

Ivan was still fit, but it was hard to call the shaggy wolf muscular still. He looked like he could be a runner, maybe, or do a lot of aerobics, but the mass was all Sam. Her chest, while not all barrel-sized like Ivan's had been, was still broad, spreading out into her thick shoulders, which supported her rippling arms. Her broad upper body narrowed down around her waist, though she had her abs and her lats to keep her sturdy even at her thinnest point. Then below that, her hips and thighs, which were as broad as her shoulders, all the way down to her strong calves and large paws.

Before Sam got too tall to reach Ivan's head, she leaned down, tugged him up, and pushed her lips against his in a forceful, hungry kiss. He groaned weakly, both spent and intimidated, but he returned the kiss.

Sam broke off the kiss when her neck started to ache, then planted her palms on the bed and let Ivan sink beneath her breasts while she drove him into her tight folds again and again. The one thing of his that hadn't shrunk was his shaft, and Sam was going to enjoy the hell out of that.

Beneath her, Sam had lost nearly all of his muscle, and was still losing height, inch by inch. His stomach was softening up a bit too—the extra weight that Sam had in the beginning had to go somewhere, after all. But while he was shrinking down to Sam's size, Sam was still growing, too big to fit on the bed if she laid out straight, tall enough that if she was wearing heels, her head might brush the ceiling. She didn't have to play anything up for Ivan—she felt savage and wild, like she could do anything she want, like if she wanted she could toss Ivan over her shoulder and cart him off like a prize she'd won.

Sam roared out loud. The headboard splintered where she was gripping it. Her muscles strained all down her arms, across her shoulders, and down her sides. Veins bulged and pulsed, and beneath her, terrified and excited, Ivan clutched at her hips and shuddered in his second orgasm.

It was something between the rush of power and the hot spurts coursing up inside of her and the sudden puff of smoke from the machine on the desk that sent Sam over the edge. She held Ivan against her like a pillow or a blanket she was snuggling, squeezing him as her body pulsed, and pulsed again, and again, and again, until she was laying on top of him, trying not to be too heavy on her smaller, slightly pudgy boyfriend. There was no way she was less than seven feet tall.

While Ivan laid there, eyes closed, panting, Sam got up to check on the machine. She popped the screws out of the bottom, lifted off the top, and spotted what had broken: one of the special capacitors she'd salvaged from the biotech equipment she'd swiped. It was blackened and surrounded by a charred ring like it'd been hit with a fireball.

It'd take some time to find a replacement, but that wasn't a big worry. It'd take some time to train Ivan back up to the point where it'd be worthwhile to use it again.

"Hey, shrimp," Sam growled, planting one foot on the bed and leaning toward Ivan. He looked almost kid-sized, she thought, but then most people would look pretty small to her at this point.

Ivan opened his eyes and swallowed dryly.

"Sam, that was…I can't…wow," he panted.

"If you want some more of this," she said, pulling her arm into a flex, making her bicep pop out, thick and rippling. "We'd better hit the gym."


Sam stood in the elevator, wearing one of Ivan's tank tops stretched over her tits and a pair of his shorts cinched up around his waist. Ivan, carrying his water bottle, hurried down the hall and into the elevator, in an old set of clothes he'd dug out that managed to fit his reduced frame.

"Lucky you've got your own personal trainer now," Sam said, grinning at him and ruffling his thick hair. The elevator doors closed and they began to slide down, but on the next floor down, it stopped.

"It's here, come on!" a girl's voice called as the door slid open. Outside the elevator, their hyena neighbor was waiting, though instead of the big butch girl, she had her hair back in a poofy ponytail and looked much more lithe and bouncy than big and bulky. She had a brighter smile than usual, and her voice was higher and peppier too. "Oh, hey!" she chirped, smiling at Sam and Ivan.

"Hey, Jess," Sam said, while Ivan just smiled.

The hyena, whose name Sam had no trouble remembering now, looked between the two of them with a small pout."Something happen to you guys too? It was super weird, we were just hanging out in our room and then…bam! And well, then we kinda started—"

At that moment, her boyfriend caught up with her. No longer a little jaguar, now he looked big, maybe almost as big as Ivan had been to begin with. He wasn't just taller and thickly muscled, either; his jaw was firmer and he had a handsome bit of scruffy fur along his chin and his hair was trimmed back into a mohawk that wasn't too far different from the kind that Jess had before.

"Oh, woah, you guys too?" he asked.

"We were just talking about that!" Jess said, leaning into his arm as he grabbed her by the hips and pulled her against his side.

"Yeah, crazy," Sam said. "But hey, you guys seem to be taking it well."

The jaguar grinned down at Jess. "Well, we kinda…took some time to enjoy it. Hope you didn't, uh—"

"Nah," Sam said. "We did the same."

Jess giggled. Ivan blushed a bit.

"We're just heading to the gym, gotta get this guy working out again." Sam gave Ivan a pinch on the ass.

The jaguar smiled. "Really? Us too."

Jess said, "I wanna give his yoga class a shot!"

"And I want to just try some lifting," the jaguar said.

Sam nodded. "Nice. See you there," she said, stepping out of the elevator as the doors slid open on the ground floor. The jaguar stepped out too, while Jess lingered in the elevator for a moment with Ivan.

"Your girlfriend is super hot," she whispered.

"I know," Ivan groaned , before following Sam out to his car.