As Katy pets the human form of Buster, her female desires get the best of her and she crawls on top of him. Slowly she slides her own vaginal opening down to meet up with Buster's cock. The eager Lab thrusts into the air with his hips as Katy gets close. Katy pauses, and puts both hands on Buster's pectorals, "Stay still" she commands. Once Buster is calm, she tries to line up her opening with his cock tip. Her plan almost works when Buster thrusts up, and slides his cock into her ass. Quickly she raises up, "Stay still Buster!" she commands louder. The second time proves a little better as she touches her opening to his cock, and with a thrust, slides in.
"Ride'em Katy" cheers Cal.
Soon Katy and Buster switch positions, with Buster thrusting into Katy with power while laying on Katy, pinning her to the floor.
Everyone was too involved in watching the mating pair to notice that Jim, Cal and Katy's father, had arrived home early and was inside the house. He had heard Cal's voice, and came to investigate. No one noticed Jim watching in the doorway.
Buster's body tensed up, and his thrusting stopped. Katy, unable to move, said, "Wow that's fun". Mark said, "OK, I'll go next", and sat up to get off the bed and said, "Shit, it's your dad."
Everyone quickly turned to the doorway, and froze, except Buster, who was still high from his first human male orgasm. After several minutes of eyes glancing, Mark said, "Want to join us?"
Jim took a deep breath and smiled, "Mark, that has to be the dumbest thing I have heard you say. What would make you think I would take part in this? You have a stranger here banging my daughter, and my son is cheering her on. I am just thinking of what I am going to tell your mother Mark, and the mother of these two here."
Mark looked at Katy and Cal, "Can you two leave so Buster and I can have a word with your father."
Jim shook his head, "No, you don't get it Mark." and walked into the room. Once he got closer, he noticed the huge canine cock between Mark's legs. Jim stared at Mark for a while. Katy pushed Buster off her with Cal's help, and Cal took the collar off buster. Jim was furious and was going to teach Mark a lesson when Cal quickly surprised his father and slid the collar around his neck. Katy and the still transforming lab watched.
Mark looked over to Cal, "I need the other piece." and then looked to Jim, who had new thoughts of lust and of enjoying what Mark had between his legs. Cal handed the dildo to Mark, and said, "I'd rather not watch. Me and Katy will wait in my room with Buster." Then Cal, Katy, and a now four-legged buster left the room, closing the door.
Mark looked at Jim, "Like what you see?"
Jim responded, "What did you do to my son? What are you going to do to me?"
Mark smiled, "Your son is now mine. And I want Cal's parents to be happy for him and me. Soon you will see. The collar has that affect. Now suck my dick, Jim." Mark lied back on the bed, and dangled his pink shaft at Jim, who's resistance was fading. Moments later, Jim was on the bed, sucking Mark's canine cock.
Mark knocked on the door over an hour later, with a very good looking Great Dane. Mark smiled, "My ass is sore and so is his." Mark reaches down and removes the collar, and hands it to Katy. They all watch as Jim slowly regains his human form, especially the huge canine cock between his legs.
Cal spoke, "Wow, my dad's huge"
Mark smiled, "And strong too, your mom is lucky. We need to all have a talk about this."
As Jim began to stand up, both Katy and Cal went to hug their father, and he hugged back. Jim spoke, "This is not the right thing to do Mark."
Mark replied, "Then we should talk about what is the right thing then. Let's go to the living room."