Rat wasn't very smart.
Well that was an understatement, the two foot tall rat mutant had a had a mostly fried rat brain that fired just about enough cylinders that she could kind of understand the big hairless monkeys around her, and communicate a few words. She was at about the level of an reasonably smart dog, with some level of talking. Her thinking process wasn't even the same as it used to be, it was more a string of feelings, images, wants, and memories strung together, actual words featured only when she thought to say something out loud.
Rat was also incredibly proud of how stupid she was, she didn't quite remember why though. All she knew was it made her feel all tingly inside, and especially how it made her sex feel. Whenever the humans called her a dumb animal, especially Eric it struck some deep chord within her that thrummed her arousal.
Rat was also disgusting.
She'd seen her body in mirrors and when looking down at herself. A mottled grey/brown agouti fur covered her body; her digits were knobbly, clawed things, ungainly and ugly; her breasts were saggy leathery duds with glossy black teats; her face was a whiskered rat muzzle with beady black eyes, a streaming wet pink nose, and a pointy snout full of rat teeth; her scaly tail trailed behind her, and she hunched on her rat legs and feet; and her sex, it was a black and pink mottled monstrosity, with a lumpy swollen clit that constantly dribbled opaque liquid behind her. She also stank of sex and rat pheromones, her breeder glands where oversized and overactive as she gleefully emptied them at every opportunity.
Rat was dumb and disgusting but she understood that she could be dumber and more disgusting, and really frustrated that she wasn't being let.
Rat remembered that eric's cock used to make yummy juice that made Rat feel better every time she drank it. She remembered vaguely a time where she was filled and pampered with as much of it that it got her to this. But now it felt different. Sure, his cock felt amazing, but it neither made her womb quicken, nor her body and mind degrade further, and that annoyed Rat.
She'd tried communicating with Eric that she wanted to go further, but he'd rebuffed her, she didn't quite understand why, something about "small".
She also remembered that the first change came from Tom-Tom's rat batter, so she'd tried him next, but she got scolded and now his cum didn't feel right. So that didn't work either.
Then yesterday she'd come across the perfect outlet, she saw another human changing from rat cum, and realized that there was much more rat cum out there. Outside of Eric and TomTom. This human had the same cum, she could smell it.
She'd wanted it so badly but again was stopped from doing anything, this time by her litter-mate! Not only that, she was taken back and scolded by her and Eric. Why were they so stupid and mean to her?
Rat may have been stupid, and disgusting; but far more than that she was horny, devious, and stubborn; and she was up to a lot more than Eric gave her credit for. She already tormented Eric's mother when he wasn't around, and often sucked off Tom-Tom just to taste his rat cum.
Rat was stupid, disgusting, stubborn and all around a vile little horny rat-creature.
Rat sat in her dark room, awkwardly cross legged, playing roughly with one teat while staring down with her nocturnal vision on the sprawled bodies of Eric and her litter-mate. Both were still sticky with perspiration mixed with sex fluids and breathing heavily. Their scents were all over each other.
Rat scowled at them, the humans were holding her back at this point, and their sex smelled like yucky human sex.
Rat was always so obedient to Eric. Why wouldn't they let her to go further? Why didn't they understand? It frustrated Rat as she sat there, letting her few brain cells slowly fizz around her head as she tried to think of something to make her feel good.
It was a tedious process for Rat, further impressing on her how much better it would be once she was dumber and could run on rat instinct alone. But bit by bit, as time ran past, she managed to put something together; pausing only once to let Tom-Tom give her a quick fuck as she connived.
'Humans were mean to Rat. Won't let Rat be more dumb... because they not know how good dumb feel... Rat must punish humans.' The thought finally completed and Rat churred in excitement, as the squeaking Tom-Tom let out his tiny issue in her comparatively huge rat vagina. As soon as she'd hoisted him back into his cage she looked down at the tiny streak of cum slimed across her vagina, then back up at the sleeping humans. Finally something clicked.
Rat had a stupid, disgusting, devious, vile, and horny plan.