Balros
Balros was babysitting for a blue-furred mousegirl. And, impossibly, when her folks got home later that night, everything was completely normal and fine. The squirrel is all smiles as he gets an envelope with his cash. He heads home. It's later that night that his corruption takes hold. Papamouse wakes up to find his moaning mouse wife is sporting a large furry sheath and balls - and his squeaking mouse daughter is her cock. The girl has merged with mom and from the waist down she's a dick, from the waist up she's a cute mousegirl, though sporting a bit of paunch, and a pair of tits that rivals her mother's. Mamamouse's own boobs have inflated with the mass of her daughter, as have her hips, thighs and paws. The two of them seem to be contesting over control of the mamamouse's body.

LlunaBlue
In reality, such a contest was much less about control than it was them confusedly pursuing more of the overwhelming pleasure that's suddenly befallen them both. Daughter-mouse bounces in the air as their hips thrust upwards, precum frothing from her agape and squeaking maw while momma-mouse's head bumps against the bed; she's as much thrusted, frothing and schlongifying as her daughter appears to be!

Balros
The shared set of nerves, linked to two different minds - it's all pleasure, up and down. Mouseballs bloat and churn with rampant production, cum spurting past cute lips to turn squeaks into gurgles. Mommamouse's legs seem to be more under her cockdaughter's control, shoving her legs into the air, fulfilling her urge to fuck. Mommamouse's hands grope and squeeze her breasts and nipples out of uncontrollable impulse. Papamouse in his horror tries to grab his daughter and pull her off his wife - only succeeding in getting them both off instead, and rewarded with a shower of mousecum in his face. He tries to pull back but his growing cockdaughter hugs him; a  tingling sensation begins as his body begins to... sink... into hers. His legs pull up and his torso tucks in; hips flare and breasts grow from his chest. Cum spurts from his lips. Soon, he's a second mousegirl cock, throbbing alongside his daughter in his wife's sheath.

LlunaBlue
The addition of new flesh only spurs the growth of the newly-forming fuckdemon; the conglomerate of mouse cock, tit and orgasmically screaming maws rubs whatever parts of itself that it can with whatever limbs it has available. The bed crumples beneath the violently thrusting and convulsing mass, waking up the dog couple living on the other side of the bedroom wall. They look to one another as the squeakings reach their ears and feel an irresistible compulsion to hold one another... and stroke... and press their hips together...