An hour later, the booth attendant leads you and your brother both out of your house on leashes. You're both running and straining, untrained and puppy-like, desperate to sniff at and pee on everything you can find. The booth attendant has her hands full keeping you under control, but somehow, she manages it.
Eventually, she gets you both to the park, and leads you to the dog run. There, she lets your brother off the leash, and he begins running loose, sniffing everything he can. But she keeps a close hand on you.
"Can't let you get loose, can I, pretty girl," the attendant says, scratching you between the ears. "I need to make sure nobody but Max ever gets up in your pretty little womb. See, in the human world, if a brother gets his sister pregnant, that's incest, and people agree it's icky. But in the doggy world, that's how we create purebreds. That's what you and your brother are, little girl, purebreds. And I aim to make sure you and all your puppies stay that way.
"See, puppies descended from transformed humans are very valuable to collectors," the attendant goes on. "Bet you didn't know that. But your puppies will be worth easily twenty, thirty thousand dollars each. As long as I can guarantee that both sire and dam used to be human, your puppies will make me very, very rich. So you'd better get used to being your brother's bitch, little girl. Because that's all you and he are anymore, breeding stock."
Over across the green, you see your brother sniffing at another dog on another woman's leash. Something deep inside you tugs: that doggy is familiar. You watch your brother walk up to this other dog and sniff at it, tentatively. The woman holding the leash gestures. Your brother rears up oh his hind legs and, right before your eyes, mounts and has sex with this other dog. You feel suddenly jealous.
"Oh, yes, look at that," the booth attendant says. "Remember your friend Becky, the one who called me a bitch? She's good breeding stock too. She'd be even better than you, with her spirit and vigor. But your brother makes you more valuable than her, because we know your genetics are pure. Becky's puppies are maybe worth about five thousand apiece, which I guess is nice. But your little puppies are the real treasure." The booth attendant scratches you behind the ears. "I hope you're okay with sharing your brother."
Finally done with Becky, your brother slips off her and runs back over toward you. The human part of you is long gone, and the doggy part of you is happy to see your mate and pack leader coming back. Oh, it will be so nice to have your brother's puppies! You hope you're already pregnant. What a good sister you are. You love being a dog.