When his changing cock suddenly grew a balooning knot that tried to lock him in his sisters vagina, a small light of resistance, deep buried within Cal's sould, burst into a scream: "STOP THIS!"
In a fluid motion, Cal got up from the chair, unsnapped the collar with his paw-chaninging hands and threw the devilish thing to a wall. He pushed Katy from his lap in the same motion, not caring to stop her from plummeting to the floor.
Cal's heart raced as he saw what his animalistic arousal had done to his body: fur had grown all ofer his skin, his arms and legs had stared to warp into a dog's legs and his penis had changed shape into a full-blown and fully errect dog cock.
"What... what have you done to me?" He screamed, directing his fearful gaze at Katy (who smiled up at him from the floor with an animalistic grin). The dogs in his mind kept mating and his arousal only seemed to got worse when he freed himself from that damned collar.
"It's no use, bro," Katy murred, "you've been touched by the beast and there is no way you'll be able to resist your new urges now." She fingerfucked her moist slit with her semi-talons while she kept grinning at Cal.
"No, no... this can't..." Cal stated fearfully while his warped fingers started to slowly move up and down on his doggy cock.
When he noticed, his eyes grew wide and he ran up the stairs naked and still changing, leaving behind his traumatized buddies and Katy, who slowly took the collar from the floor.
"This will be interesting," she growled and snapped the collar around her neck again.