Just as Lady's identity was now fully canine, Marcy's was fully female. As a loyal if inexperienced member of Team Girl, she knew that Dustin's love of bullying the weak would make him an abusive boyfriend at best, a batterer or even a murderer at worst. She would change him back into a man, but there were going to be some modifications, and seeing the enthusiasm of dog Dustin for sex gave her an idea.
Dustin now had a dog fetish. Although his memory of his brief time as a stud dog would be fuzzy, there would continue to be a strong association between being a dog and sexual pleasure. He would seek out women who would treat him like a dog, putting him on a collar and leash, taking him for walks, swatting his rear when he was bad, and serving him food in a dog dish on the floor. In return he would treat his mistresses as would any loyal dog. He might even seek biological modifications to make himself more doglike.
Marcy teleported human Dustin back to his bedroom. As a parting gift she left a leash, a collar with a tag bearing the name "Dustin" and a monogrammed dog dish on his nightstand.