As Katy was able to speak, she asked Cal, "What do you mean? Don't hurt Buster."
Cal smiled to his sister, "I won't Katy, in fact I am curious to see what happens with a Labrador Retriever."
Mark gives an occasional thrust of his hips inside the large canine, "You have to wait until I'm done."
"You don't have to worry about competition from Buster, he clearly enjoys having you inside him." says Cal as he notices Buster's well sized cock is now fully extended again.
The three talk about how their lives are changed, and only stop when they notice Mark stand up, not noticing Mark had slid out of Buster.
"OK Cal, your turn." said a satisfied Mark, who went over to the bed to lie down. Katy crawled up on the bed, and over Mark.
"Can we, again?" asked Katy.
"Sure" replied Mark, and enjoyed the next couple of minutes as Katy did all the work until his knot expanded inside her.
Tired of waiting, Cal asked, "Katy, did you want to see this or not?"
A slightly panting Katy said, "Go ahead, I'm watching"
Cal proceed to whisper into Buster's ear. Cal reasoned that if he could tell Buster what to think, Buster's transformation would match. Cal didn't realize that Buster didn't understand English. Cal slid the dildo from his pussy, and slid it into the labs stretched ass. After a few thrusts, Buster began to change.
"You better watch this Katy" called out Cal as he continued to slide the dildo repeatedly into the changing Labrador. As the Lab's torso began to change, the legs began to shift, and the large lab's muzzle began to shrink into his face. After a few minutes, Cal slid the dildo out of Buster's pink, human anus. Katy and Mark stared at the nearly 6 foot tall super athlete body that lay on the floor. Buster's pale white skin seemed almost alien, except for the huge cock and balls that throbbed between his legs. Cal slipped the dildo back into his own vagina, as he loved how it felt.
"Me first" cried Katy. She quickly raised herself off Mark's shaft, slide off the bed, and on to the floor next to Buster. Katy then began to pet her now human friend.