Collaborative sex stories let us write the plot together

(Medical Experiments, continued by RandomShadfan...)

“Well, what have we here?” You hear a new voice behind you, but you’re strangely not afraid.

“Doctor Mandy! It’s just — ah fuck — I wanted to apologize for the — ungh — effect of the serum,” Jenny lies, but she’s having trouble speaking as you’re still fucking her. “The serum turned — oh god — Steve here into this man-dog and — ah yes — he told me I was sexy as hell. I figured this — oh! — was the best way to say sorry.”

Doctor Mandy smiles at Jenny in answer. “Oh, Jenny. A tart then, a tart now, a tart forever,” she comments.

You suddenly become aware that your dog-penis is starting to swell slightly, and the combined scent of Jenny and Mandy is driving you over the edge, fast. Half of your brain wants to cum inside Jenny’s pussy, but another part wants to try out Mandy’s first.