"Okay boy, you're not going to understand this but we need to to a physical exam to make sure that injection we gave you turned you out right. After we're sure it works, then we won't need to examine your brothers.
You bark happily at the human as he leads you into the next room. He's right, you have no idea what he's talking about. He leads you onto a medical table. The room has all kinds of posters of the canine anatomy, one of these guys must be a veterinarian, probably the one in here with you. He opens your jaw and looks inside, feels your teeth, looks in your ears, examines your eyes, takes your temperature, looks through your fur.
"You're a doberman, male, about one and a half years old, weight average, size average..." He calls these things out in his odd human language as you pant and give the occasional bark. Then you feel something really weird as one of his gloved fingers enters your anus quickly, wiggling around.
"Prostate normal..."
He then fondles your testicles, making your canine member come out of its sheath, which he examines.
"Yup, you're a dog all right." He says finally. "100% complete transformation, amazing! This is an unprecedented breakthrough. Now, since you're our first test subject, we're going to do our best to ensure you enjoy being a dog. Some of this will be unpleasant, but you'll manage. To think how the world will be changed by this research, this level of genetic manipulation. Boy, you're going to save lives." He says, scratching you behind the ears. without really knowing or caring what he said, you lick his hand lovingly.
"Kyle, I've made a fascinating discovery!" The scientist guy shouts as he comes into the room, with two dogs following behind him. Both dogs are golder retrievers. "It seems the Canus Supremus serum cause transformation into a different species based on genetics."
"That's amazing Mr. Parkman!" Kyle says.
"Indeed! Look how the one brother becomes a doberman, yet these two genetically identical twins each become retrievers! You know what this means!?" Mr. Parkman pauses, then answers his own question.
"It means our work is just beginning. We need to test which genetic patterns cause which species, as well as how the genes of each transformed person are affected! Oh we have so much to do!"
"What about the funding?" Kyle asks.
"Never mind the funding!" Dr. Parkman says as he walks into another room.
All this while you have been getting to know the other two dogs. First you sniff both of their butts, and they do the same. Then the three of you lick each other. Some how they feel so friendly to you, so familiar. You even know their scents, and they know yours. Kyle bend down and pets the three of you. You're quickly starting to like him.
"Since the three of you are dogs now, I think you could use new names." He then thinks up names for each of you, and actually makes little metallic tags to attach to each of your collars. He calls you "Spike". Your brother Tad becomes "Blaze", and Chad is called "Chad", because Kyle runs out of dog names. Finally he leads the three of you into a kennel, complete with doggy beds, water and food bowls, and toys.