It took 2 days, well over 52 hours, of constant sex for Smelly Rat to get to her and Eric's desired form.
Their initial sessions were quick, frantic affairs. Eric taking Smelly Rat wherever their rough coupling took them. Banging and knocking everything over as they pawed at each other, both panting and giddily excited at what they were doing.
Right around the time Smelly Rat's tail had started growing in, and her head hair turned a rat grey, Eric began running out of steam. Insisting they continue, Smelly Rat made him use the Chronivac to give himself unending stamina.
Re-invigorated, he pounced on her, trapping her under him as he pounded her, pumping wave after wave of transformative cum into her abused pussy. Her growing tail snaking into the pool of rat cum spreading under them.
A few more hours under Eric and her breasts began to deflate and sag, nipples lengthening into teats. Along with this her feet lengthened, toes elongating to tipped claws.
Around this time Smelly Rat completely stopped referring to herself in the first person, all of her frantic shouting and begging referring to "Smelly Rat *this*, and Smelly Rat *that*."
Hunger and thirst eventually stopped this phase of their rutting as Smelly Rat, driven by need, turned the tables and flipped Eric, grabbing his Rat cock and wrapping her lips around it, sucking and swallowing every drop it issued forth.
A recovering Eric watched as a gasping Smelly Rat filled her needy belly with pints of his tarnished semen. First her pot belly distended, full to the brim with semen. Then he watched, in ecstatic awe as over some hours his human faced girlfriends lips deflated, her nose pinched up, and her mouth slowly distended into a rat muzzle.
Scraping buck teeth eventually forced Eric to pop Smelly Rat off his cock. The creature that spoke then sounded nothing like the girly voice she'd had before. Instead scratchy, shrill barks of delight belched from Smelly Rat.
It was at this point, listening to Smelly Rat's utterances, and coming up on 18 hours, and many hours since her face began changing in that the decline in her mental faculties registered with Eric.
Grammar had gone out the window, as had any long statements of higher thought or ponderings. Smelly Rat simply stated her wants or thoughts in simple short bursts.
Her utterance "Smelly Rat face feel gooder now. More filthy-good... Disgusting yum-yum good." As she burped, rubbing her distended, cum filled pot belly, made Eric pause long enough to inquire on her decreasing intelligence, and was momentarily worried what they were doing. Her response set him straight, reminded him that changes were permanent, and all together to late to regret now.
"Yes. Smelly Rat feel the dumb-dumb come when drink the yum-yum juice. Excite when feel dumb-dumb come. So happy drink more yum-yum. Smelly Rat smart-know dumb-dumb good. Make Smelly Rat more rat. Want more yum-yum to make the dumb-dumb more, Smelly Rat still too smart...". At that point the creature, getting more frantically excited spied the cold puddle of soaked cum deposited on the floor hours before; squeaked in excitement. "FILTHY YUM-YUM". She screeched, diving onto all fours and began hungrily lapping up what sticky strands she could.
The inviting ass in front of him was too much then for Eric as he spread Smelly Rat's cheeks, noting how furry her ass crack had gotten. Her sweaty ass was also the first time Eric noticed a change in how she smelled. A hint of gamey-earthiness rising through.
With a delighted squeaking in response, Eric pressed the tip of his rat cock into the rosebud of Smelly Rat's inviting anus. Immediately starting the process of filling her from the bottom up.
Rounding out the end of the first day had Smelly Rat lick the floor as clean as she could, while Eric absolutely filled her digestive system full of cum, watching the fur spread across her back and sides. By the time Smelly Rat squeaked a wretched, "No yum-yum for Smelly. Not happy dumb-dumb yet. Stinky want... *Squeak* hnnnggh... Dumb more!!!", Eric knew any vestiges of Lisa were not going to last the night. He truly would be left with a dumb, filthy, sex-crazed, rat-creature, where once he had a smart, beautiful girlfriend.
A quick enthusiastic mouth clean of his cock by Smelly Rat took him out of reverie, as she held his cock with hands getting hairier by the minute. Ready of more pleasure, Smelly Rat next hopped up on the bed, spreading her legs to reveal an absolute torrent of female rat grool dribbling from her sex. It was almost like she was pissing herself, only it was far to viscous, and reeked of the gamey-earthy scent, although her vaginal lips still had human shape underneath the spreading fur.
The function of her torrential grool production became clear over the next half a day, as her body used it to shed mass, shrinking her frame down hour by hour.
By the time the sun set that day Smelly Rat was well under 4 foot tall, closer to 3, and light as a feather. A fact Eric began to use in lifting her and fucking her up against every object he could as she happily squeaked and pawed at him. Grey fur had engulfed her entirely at this point, whiskers growing, her vaginal lips had melted into a puffy slit, enormous clit pulsing; and as her profile slowly began to change from human-shaped, and her eyes turned a beady black, her endless squeaks grew more deranged.
"Yes-fuck!!! Rat dumb. More Rat. More dumb! More fuck. Rat. Filthy!!!! Feel dumb. Stinky. Rat-yessss! Hnnngghh.. Disgusting... Rat... Fuck Rat. Fuck fuck. *Squeak* Fuck Rat. Rat fuck. *Squeak* Fuck dumb. Rat tit! Yes-*squeak*yes. Small. Make small. *Hnnnggh* more small. Small rat!!! Fuck Rat! Happy fuck. Happy more! More dumb! *Squeak*. Filthy stinky. Dumb stinky!!! Yes-yes! Hairy stinky! Hairy rat... *Squeak* hairy fuck. Fuck Rat. Fuck small".
Round and round it went as she screeched her demands of becoming smaller, hairier, smellier, dirtier, rattier, and dumber. Lisa was long gone, as was even what Smelly Rat had been these past few months. Word by word, minute by minute, hour by hour, stripped away gleefully to leave a simple short, hairy, vile, filthy, dumb, rat-creature.
As the final half a day progressed, and Smelly Rat's form took that of the fateful 3 foot tall Rat-creature, Eric came to the conclusion that even referring to this thing as "Smelly Rat", or even as "she or her", didn't feel appropriate. This was a rat-creature, an "it", just...
Just a "Rat".
So he started referring to Smelly Rat simply as "Rat". Scooping up the creature and bringing it back to the computer and showing it the image that started this.
"That's what you agreed to Rat." He said pointing at the screen as the squirming creature squinted at the screen. It barked a delighted, "Rat!!! Rat-Rat!!!". Possibly recognising itself.
"I warned you you'd lose intelligence." He said, Rat simply making a puzzled face. "You're dumb..." He repeated, to which it cackled, "Dumb! Rat! Dumb!".
"You can never change back!" He added. "Rat forever" quickly, to help it understand. Rat squirmed out of his hold and dropped to the floor, hunched and happily spun. "Rat! Rat! Yesh!"
She had lost all ability to even string two words together to convey thought "You are disgusting!"
"Yesh!"
"You're a filthy Rat.
"Fil-tee"
"You'll never graduate school, get a job, marry, anything... You'll just be a filthy Rat, fucking forever. All for me"
"Fuck!!!", it excitedly bounced
"Thank you, we can stop now" he said, fully sure it wouldn't understand, but was surprised when it stopped fidgeting for a moment.
He watched as the Rat creature slowly turned, looking from him, to the screen, to itself, to its reflection, back up at him.
Next it screwed up its face, as if was using every available ounce of thinking. Eyes screwing shut it finally got out.
"Happy... Rat... Happy... Dumb! Want... *Squeak*. Rat... *Squeak*" it looked annoyed now. Like it wanted something out. "Want... More!!! More Rat!" It opened its black eyes suddenly as it managed to form the thought and words to convey her wants.
"You're already what we had planned!" Eric exclaimed. To which it just simply happily bounced. "More Rat! More Rat!"
Saggy duds flopping all over the place, thick tail slapping on the ground. Turning to the computer Eric keyed the slider, pushing her transformation forward a bit on the image
Eric's rat cock immediately shot from the sheath again, and grinning he turned
"More Rat?" He asked,
"More Rat!!!!" The disgusting creature answered.
So they found themselves near dawn of the second night. Lisa devolved into nothing more than a half bipedal, 2 foot tall, sex-crazed rat mutant, with a bare vocabulary of a half dozen garbled words.
As Eric, exhausted, finally switched off the ability of his cum to further permanently change the Rat creature, it was because it was beginning to get difficult for him to even fit his cock in it.
Turning back from the Chronivac he saw that it was already flipped in its back, hind legs spread, duds and teats puffed up, spreading its small snatch with rat paws, drooling cum from their last coupling.
"F-uchk" it squeaked, grinning...