Tails was down in his workshop, working on his latest invention. "At last! I've finished!" He said, lifting his welding shield. He wiped the seat off of his brow and walked over to get a rag to clean himself up.

Tails had just invented a genetic transformation machine. By using particles from a chaos emerald, DNA and Protein synthesis could be altered, along with brain wave manipulation. The only problem? Because of the Chaos emerald's instability, the alterations that took place were not COMPLETELY under Tail's control

"I guess the only question now is who to test it on." Tails said to himself, "If I use it on myself, there's no chance of anyone else getting in danger, but there won't be anyone to help if something goes wrong."

Who does Tails test his machine on?

*

maybe i shood yous myself to tast it tails said so thinking what shood i do to myself shood i....

*

"I know, I'll go with an easy change on myself first" Said Tails absent mindly to himself

He then presses the switch gender button and climbs into the machine.

He feels kind of itchy at first on his chest as his boobs eventually settle at a large, but not uncomfortable size on his, now swiftly becoming her, chest.

Then he feels a sort of tug on his dick and balls as they are sucked inside him. The hole where they were then swiftly rearranges into functional female genitals.

Finally, her figure adjusts into an hourglass shape and her ass expands.

Overall she has a figure quite like Amy Rose, but in sexy orange fox form.

"I guess I'll call myself Milly until I change back" mused Tails.

*

Tails could not resist the memory of her previous body. She used the machine again, feeling its power inside her pussy. Her vagina sealed, but her clitoris pushed out, out, out, plumping up into a familiar penis. Her pussy bulged beneath the modest cock as she stroked it, feeling it throb and grow stiff. Still, her groin expanded, a bulb beneath her shaft growing into a pair of testicles. "Ah, just like old times," Tails said, her voice high and girly. "But y'know, I think I could use an upgrade... I am a scientist after all," she giggled, and punched another command into the machine and spread her legs, feeling the warm glow envelope her groin. She rubbed one of her big breasts, the other worked her average cock, which vibrated in her hand. It was already weeping precum. She gasped, feeling her biology strengthening, her balls getting heavier with cum, heavier with need. She stroked faster, but felt her arm get weak. It was getting hard to keep up, each rep had gotten longer as her cock grew longer! The machine stopped, leaving Tails impressively hung. It must've been 10 inches long at least. It looked titanic on a body her size! The strange buzzing sensation remained. Little 'oohs' and 'ahs' escaped her lips as her pace increased, she rubbed her fat nuts, arms pressing into the sides of her nearly-Rouge-sized knockers. She froze up, clenching her hand-filling balls and let loose a wild salvo of cum shots that sailed clear across the workshop. One glop even caught one of the log-recording video cameras on the eye. "Oh wow," Tails wheezed, sweat rolling down her body, her big dong bobbing in time with her heartbeat, "I-I might have to try some more of that later..." Tails gathered herself, stumbling to wash herself off and wondered what to do next...

Tails licked her lips as she pored over her program, modifying the energy projection. The anticipation was killing her! So much so that she had taken to wearing condoms to keep from leaking precum everywhere while she modified the machine's delicate ray emitters. She had quite the collection of tied-off condoms, like water balloons full of semen, littered in the corners of the room.
Any later and she'd have resorted to dragging a bucket along with her.
She shivered all over and hit the switch, watching the tips of the beam emitters warm up and project out distinctively gelatinous rings. They slid over her semi-firm dick. Tails leaned back and spread her legs, allowing the machine to encase her shaft in a warm, glowing donut that ran up and down her length. A second one floated beneath her and started warming her sac with the same repetitive pumping motion. The glow filled her flesh with a vaguely blue color, and the rings appeared to become more solid, even pinching down on her slightly. The rings milked her steadily as she whimpered and delighted in the toe-curling blowjob the chaos-rings were giving her.
Tails massaged her breasts, watching the camera feed on a nearby monitor and occasionally glanced down at her penis, noticing that she was pre-cumming less, but every time she did, it felt like a geyser. 
"Ohhhh gosh, here it comes. I can feel it," Tails rasped, resting her hands on either side of her groin, feeling the trembling, bubbling sensation... There it was! As the plump, glowing ring pulled on her cock, it began to lengthen and thicken. It felt distinctively heavier after a few inches got blown into it, like a floppy baseball bat were hanging off her groin. The tingling sensation only intensified as the ring petting her nuts gripped firmly, slowing its pumping motion down. The heat soaked in deep. A wet sensation flowed over and into her balls. She groped them and felt their expansion in her fingertips. They pushed her fingertips further apart until it felt like she was holding grapefruit. 
The rings continued their work and Tails laid back on the examination bed with her ass aimed off the edge, letting the beam emitters have their way with her junk. They stroked energy down deep inside, sliding pulses over her taint and deep into her prostate. Pressure rose within her, her inner plumbing getting an augmentation as well. That was why every shot of pre-cum was getting larger and more intense.
Tails rest her palm on her lower abdomen, and could feel a subtle bulge growing if she pressed deep enough. It was her prostate surely, and some other plumbing that made her dick flex hard in spite of its ridiculous weight.
Her penis was gigantic. Long, but thick, flexing in the air. It had an almost muscular look to it from the few fat veins throbbing out from its surface, and as the ring firmly squeezed upward, those veins flared. A few new ones would branch out, pumping even more size into her dick. It towered over her lap, reaching twenty inches. Her balls hung lower as the cum factories they contained filled ever larger. They'd grown to a pair of volleyballs now. 
That was when the program began to spool down, and as the excess energy dissipated after the emitters stopped, the residual power flowed up her shaft, pumping one last glut of size into it. Tails' dick topped out at an impressive 25 inches.

Tails was gasping and sighing, bathed in pleasure. She slowly closed her legs, getting adjusted to how monstrously hung she made herself. She stood up, waving her massive cock around, slinging a constant flow of precum around and delighted in the clumsy weight as her soft ballsac rolled over her thighs. The root of her cock felt like an invasive clench on her groin.
She bent over and looked at how bulbous her taint was. It overfilled her thigh gap and it was so spongey. When she squeezed it, she grinned and felt her cheeks flush. Pleasure washed over her and her cock momentarily stiffened up, grazing her breasts firmly. The amount of cum that pumped out of her shot clear across the laboratory. At least 30 feet. It sounded like someone spraying a garden hose full of glop.
"Hhggghn! Th..that was.. incredible!" Tails whined, watching her enormous dick go semi-firm again. It was wildly sensitive, springing to full erection at so much as a breeze, but she had to calm down so she could... 'review' the footage of her transformation over and over again.

She popped the recording out of the terminal feed and carried it with her to the bathroom, where she narcissistically masturbated to the sight of her own dick getting pumped up. Her bathtub drain could just barely keep up, filled to the lip with gallons of potent semen. But at least she could relax enough to take an actual shower, letting the hot, prickly water rinse the stink of sex away. She toweled off, and bit her lip as she clothed. 
She did pick out spandex clothes for such an occasion, but underestimated herself when the groin was involved... With a little bit of talcum powder to make her junk more slippery, she managed to slide her fat, soft python into the groin, where it immediately plunged down one of her pantlegs while her massive volley-balls bulged out over her lap.
Tails blushed at the obscenity bulging through her stretchy leggings. It was almost worse than going totally nude. She could keep her big breasts modest, even on her rather lithe body. Still, she was seriously regretting having no long skirt to wear. 

Milly decided to fuck Amy, but she needed to be here first, so Milly called her phone. After several rings, Amy picked up. "Hello?" Amy's response was not in a kind tone. "Who is this, why do you have Tails' phone?" Milly realized that she needed to explain this to her. "Amy, it's me, Tails. I made a transformation machine, could you come to mine so I can show you?" Amy agreed and within 20 minutes, Milly was letting Amy in. "Tails, what did you do to yourself?" She asked as she saw Milly's figure. "I transformed myself, there's something I want to show you privately." Milly lead Amy up to her room, where she revealed her huge cock, making Amy gasp in surprise. "I... I can't believe it. It's so big, can... can I touch it?" Tails...

They were still in the lab, Tails seated next to Amy on a spare couch. Tails hadn't wanted to shock Amy too badly, so she'd dressed up. Nothing quite fit right, and Tails was horny when she'd called Amy over. Amy looked curious, but unsure. She was so fascinated by the change and offered to touch the futa-fox's bulging boxers. Amy's eyes kept wandering over Tails impressive jugs. The shirt didn't fit and the checkerboard pattern stretched sideways over her enormous balloons. Her nipples were grossly enormous, bulging out a few inches. They looked like puckered doorknobs.  "Y-yeah, you can if you wanna!" Tails gasped, failing to hide her surprise at Amy's fowardness. He spread his legs and leaned back on the couch.  "W..Wow, if you can.. D-do this, then maybe I can.. It's real!" Amy exclaimed, lightly peeling down Tails' shorts, looking at the lightly veined shaft. She slid it out and cupped Tails' fat nuts, blushing at how a single one filled her hand. "They're so heavy, Tails.. Whatever you did, it's gonna be a hit with everybody wanting a new body," Amy giggled. She was practically glowing pink all over. Tails was incredibly horny, writing around on the couch, starting to glisten. Her dick began oozing precum, which Amy didn't shy away from. Infact, she knelt forward. Tails' eyes widened, looking over her own bosom as Amy kissed the tip of her dick. It throbbed painfully, rising up into a stiff arch. Tails vision became blurry and Amy's gentle humming buzzed vibrations at the tip of her wide glans. "Ah.. ahhhh Amy!" Tails whined, reaching up, but Amy planted a hand on Tails' breast, lightly fondling one of her engorged nipples. Tails shuddered all over, biting her lip, smiling. She fell into a limp, writhing puddle. Amy smiled, petting Tails cheek and licked her own lips, saying, "You taste as sweet as you look, cutie." She danced her fingers up and down Tails' 25 inch dick, which throbbed so much it swung back and slapped Tails' belly until Amy actually groped it. She leaned into it, blowing on it, teasing it with her warm breath. Tails arched her back under the tease, feeling like she might cum if it went on. Wet, jittering pleasure rode up her cock. Her eyes closed, but nothing happened. The tension released gradually and her breathing became even again. Amy smiled, gazing over her shorter partner, letting Tails stew in a pool of her own sexual glaze for a few minutes. She realized exactly how sensitive Tails was, and wondered...
Amy knew Tails was putty in her hands. The way Tails writhed around, it almost seemed like she had no sense of herself.

"It feels that good, huh Tails?" Amy whispered, rubbing her open palm against Tails' fat nuts.

"C..Call m-me Milly," Tai..Milly whimpered. Amy grinned, laying down beside Milly and rubbed the fox's face against her bosom.

"Of course, Milly. That's cute," Amy giggled, and slathered her hand in more of the foxgirl's precum. Amy stroked Milly's fat dick, milking out more and more precum.

"It's a play on your first name. I like it a lot," Amy said, kissing the tips of her fox ears. She writhed in Amy's lap, twitching as pleasurable sensation fired off in her body. Her dick already felt a sort of raw oversensitivity and Amy knew it, always intuiting the right moment to ease her stroking before Milly really let an orgasm follow completely through.

Amy whispered, "Try to hold on.. Don't cum yet, Foxy." Milly nodded, pressing her face into Amy's modest bust. Amy smiled, rolling her fingertip around the constantly oozing tip of Milly's dick and noticed that its throbbing had steadied.
"Just like that," Amy whispered, and gripped that 25 inch long cock and started squeezing firmly. Veins flared up over the shaft and as Amy stroked up slowly, it began to swell fatter still.

Milly gasped. Her voice was shivering and borderline pained. Amy's eyes widened, watching the fox's phallus elongate by a full inch. When she released, it went down to normal. 

She had to try again.

Amy groped the bottom of Tails.. Milly's dick in one hand and stroked upward. Again, it expanded. In her other hand, she clamped down on the root of the cock and released, noticing it didn't shrink at all. Milly's shaft looked very healthy. She stroked up slowly a second time, watching it expand a foot longer. 37 throbbing inches.

Amy repeated the process. Milly was arching her back and Amy knew she had to ease off.
"Aaaaammmyyy.. I'm.. I'm gonna," she begged, but Amy replied, "No-no-no. Relax. Breathe deeply, Fox Face."

She groaned and buried her nose in Amy's breast. Her dick lurched, but she didn't cum. The moment was tense. Her eyes were locked on the tip of Tails' dick, waiting for the explosion but the girl kept it under control. Amy finally realized her hands had been off Milly's junk all the while and it had retained its newfound size, too.

Amy grinned, and said, "Okay, Milly.. I want you to jerk off for me. Nice and slow."

Milly sat up, trembling all over. She obeyed, not aware that her dick had swollen up by another two extra inches. It didn't grow... Maybe the technique was wrong? In any case, Milly was loving it, pumping out a ridiculous amount of precum. It seemed like the fox was a bottomless well.

Amy molested Milly's breasts, a bit jealous that they were so much larger than her own boobs. She moaned in turn, and Amy could feel her heartbeat rise again, could hear her voice become more pained again. She wanted to cum so badly.

"Patience, Fox Face," Amy grinned, twisting her fat nipples. Milly leaned into Amy's groping hands, and she gasped. Her tits were enlarging. It was slow, but she felt it. They pressed more earnestly against her hands.

"A..Amy, I.. I'm g..growing!" Milly exclaimed. Her hands shot up to her tits, and the heat radiating from her chest intensified. Her long dong arched up and slapped against her chest, an additional two inches had swollen up its length. It had thickened rather significantly too, and bobbed in the air as it throbbed.

With their combined attention, Milly's breasts expanded rapidly. She was lithe already, so her bust quickly overcame her torso. Her shirt was drawn snug over her overdeveloped bosom.

"Hh..hahh.. Amy.. This is so hot.. M..More.. M..ore," Milly whimpered, watching her tits rise to the size of basketballs on her lean body. Amy grinned, knowing how to really get Milly "Tails" Prower to get a thrill and rubbed her back. Slowly, her fingertips fanned out to the sides of the futa fox's torso and touched her breasts from behind.

That instantly gave Tails the mental image of seeing herself from behind. Her breasts were so girthy, so wide, that they could be seen from behind. She looked down, unable to see beneath her humongously swollen bosom. 

Amy grinned, and stood Tails up while saying, "I think you've earned this." She walked the horny fox over to her test chamber, where cameras were set up, where the two of them could see Milly's new body from every angle.

Milly was constantly panting and swung her massive breasts around and slowly masturbated. Every time she was about to cum, her knees trembled, her hands fell away from her dick, and it expanded steadily. Every time it happened, Milly had to flex harder and harder to keep from letting her jizz loose. It wasn't until she was able to see in the cameras that her nuts had ballooned every time it happened, filling her nutsac out with their increased mass.

"Good girl..." Amy grinned. "Mmm, mmm, mmm, Milly. We need to get you to blow off some steam! You look so stressed out!" Amy chided, and threw Tails, though she preferred to be called Milly now, a duffel bag of loose fit clothes.

Milly was a well-endowed dickgirl, having exposed herself to a transformational ray and was reeling from the effects of it. Her libido was wild. The more pent up she got, the bigger her cock and balls grew. Amy was fully aware of it, and now wanted to see how Milly held up under pressure.

Gradually, Milly calmed down, and slid into the new clothes. Jersey-style material that draped comfortably over her pornstar curves. Her breasts were as big as her head, and could easily be seen from behind. She was quite slender, though her hips exploded outward and strained the waistband of her shorts. Her hefty package wobbled out in front of her provocatively as she strode.

Milly was blushing already, focusing all her attention on not getting any hornier, lest she go off before she'd like. She and Amy caught a train to the gym in Central City. Milly held her gym bag on her lap constantly, attached at the hip to Amy to try and conceal herself from prying eyes that admired the deep, soft, creamy cleavage wobbling beneath the jersey top.

"Oh, relax, Foxface!" Amy said, pecking Milly "Tails" Prower on the cheek again and again. "You look adorable! Just fine! And see? Just a few more minutes and we're there!"

It was a short walk from the station to the gym, which was packed at all hours of the day. Why did Amy have to choose late afternoon though? It was so busy! And all the gym rats were there at the same time, too! So many attractive people glistening. So many tight curves undulating and dancing. Milly shuddered all over and Amy had already pulled her onto a treadmill in the corner, so that they could 'look at their technique' in the mirror while they jogged.

"Keep up the rhythm! I wanna see if you can keep up with me later, too!" Amy giggled, putting the fox futa to work. It wasn't long until Milly was feeling her cock get semi again. Her shorts tented out, the floppy, half-hard cock swinging across her hips. Why hadn't she put on tighter underwear beforehand?

It didn't seem like anyone noticed, given the liberated sexuality already on display, but to Milly, she was exposed.

"Wow, Milly, I didn't know working out was soooooo exciting! Let's do a cool down, ok?" Amy said, pulling Milly off the treadmill by her waistband. As they walked to the aerobics section, Amy nakedly pulled Milly by her floppy dick, and she walked stiffly, eyes darting around while more blood tried to pump into her shaft. She panted openly, sweat drooling down her body.

It was already time for yoga. Milly didn't know any of the positions, and Amy's teasing snicker didn't help at all.

"Just follow what they do and stay close to me, okay," Amy giggled. They stretched, they bent. They spread their legs, and then Amy bumped her ass against Milly's groin firmly whenever all the other patrons had their heads down.

Milly squeaked, feeling her body light on fire. Her dick pumped into full erection, tenting the loose cloth out so much that the waistband lifted from her belly, too!

Amy kept Milly's huge cock concealed though, and turned to face her, grinning deviously and whispered commands to her," Good. Follow along with me. We're doing partnered stuff now. It's fun."

Amy pressed her feet to Milly's as they sat down, and her palms to the insides of the fox futa's plump thighs. Wider and wider their legs spread, until they were pressed up against eachother, both doing splits. Amy necked with Tails, kissing her neck, and slowly rubbed the root of her pet fox's cock, causing it to slowly swell larger.

"Okay, that'll be all for today. Another lesson will resume tomorrow," the instructor trailed off, and most people stood up and filed out. Amy stood up in front of Tails. Tails pressed firmly behind Amy, her huge cock running up her back, and they left last.

Tails shuddered all over, whimpering, calming down to get half hard, but her cock had grown. She felt it expand. Amy rushed ahead, grinning, knowing Tails would follow. Her dick swung out in front of her, barely contained in her jersey shorts. She could feel her potent cum dribbling out. 

Everyone could see it, she knew it.

Some people did, but they were just shocked enough to want to watch more and tell nobody about the more than horse-hung girly girl prancing around the gym.

Amy directed Tails to an upper body workout machine and grinned widely. Tails sat down and Amy took a seat on Tails' thigh, spreading her legs across the length of Tails' stiffening cock and said, "Good girl, Milly foxie. Now I want you to envision your chest getting bigger as you work your upper body. Do you know what I mean?"

Amy made it abundantly clear by leaning in, pressing her shoulder against Tails' rather enormous breasts. Tails nervously pressed her forearms against the arms of the machine. Amy leaned behind her and set the weight. She continued to sit on Tails' lap, since her huge cock was peeking out of the end of her shorts, swollen to a massive length of 42 inches or so. Beneath her pink thighs, Tails was concealed...

"One, two, three," Milly counted, pumping the mild weight and felt the burning in her arms and chest.

Amy grinned, "Now envision that burning sensation oozing into your breasts, filling them with more power. Just like your muscles."

"Th..that doesn't make sense, Amy," Milly complained, but found herself fantasizing about it anyway. Her nipples got hard, poking out the shiny black jersey top distinctively. She looked at herself in the mirror and Amy noticed.

"Look at yourself. Imagine each time you pump your arms, you're pumping up these juicy jugs, Milly," Amy teased, rubbing her sensitive breasts just before she resumed her workout. She still didn't believe Amy, but Tails found that her reflection changed.. The reflection's bustline enlarged. As Tails pumped and pumped, she looked down, gasping excitedly. Her breasts were swelling from arousal alone, and Amy grinned, stepping away to let her stare at herself.

Tails continued to work out, getting sweatier, watching her jersey top tighten, feeling the fabric become strict around the small of her back as her heavy, jiggly tits expanded. They slid across her chest as they fattened up. Amy tipped a bottle to Tails' lips and she drank involuntarily. Some protein drink that filled her belly with the energy she desperately needed.

"Good job, Milly! Dig deep!" Amy cheered, grinning as Tails' dick tented out her shorts so much that it was like a fleshy baseball bat were jammed into her clothes. People were staring openly now, even recording video with their phones at the horny fox futa. 

Her huge breasts were showing plenty of creamy underboob, outgrowing the silky jersey. Tails had some semblance of awareness that she was being watched, but now she was just riding that blurry excitement. Some of the patrons were rooting for her when her arms trembled in exhaustion.

Her heavy breasts left her incredibly top-heavy, swollen well beyond the size of her head, dominating her slender torso and heaving up and down as she gasped for air. Amy stroked her huge dick, encouraging it swell out to 48 inches.

It wasn't long until Amy and Tails were just having sex in public. She pulled down her shorts and mounted her. The entire length didn't fit, but Tails held onto Amy's hips as she rode her, getting a little deeper every time. Her huge, thick cock packed the space between her thighs, stretched her pussy, and bulged out her belly.

The audience cheered to go to the hilt! They tried and tried, never quite making it, but Tails gave it her best shot and often thrust so hard that she pushed Amy off the ground with her! They were still seated on the machine and Amy rocked against Tails' huge, pillowy tits.

Tails nearly came inside of Amy. Amy shuddered all over and visibly orgasmed, giving a satisfied yelp. The owner of the gym was taking notice of the commotion and thought a fight had broken out. The crowd was so dense that Tails and Amy had time to cool down, regroup, re-robe, and get away... Though Tails' huge breasts bouncing around on her rail thin torso and flopping mega-sized cock complicated her escape somewhat.

Down the street they went, hoping nobody shared their illicit sex tapes with the owner. Lots of people rubbernecked, staring at the semen-stained Amy and the bouncy, astonishingly hung fox girl.

The train ride home was awkward. While the gym bags could cover Tails' lap, everyone still gazed at her chest blimps, marveling at their perkiness and massive areolae and nipples. Each one was the size of a medicine ball at least.

At home, Tails threw off her clothes and collapsed in bed, getting horny again. She writhed around in bed, feeling her big fat nuts throb in pain as they grew fatter with cum.

"You did great, Milly. Look at how swole you got, "Amy teased, flopping in bed beside her, petting her, molesting her huge breasts and laid herself across her soft chest, kissing at the underside of Tails' jaw.

"A..Amy.. C..can I.. Can I cum.. I'm s..sooo full," Tails begged, feeling her cock raise up, looking larger than ever. Amy pressed her foot against Tails' cock and giggled.

"I'll think about it."