It took ten more minutes for you and your giant bull dad to finish your shower. Eventually, you dad reached around you to turn of the water and lifted you off his dick. His fat spongy cockhead popped out of your hole audibly. He set you down to the floor, only to slide his hands up from the back of your thighs to your asscheeks and gave them another tight squeeze.
"Come on sport," he said with a smile. The two of you walked out of the shower and your dad held you close as he dried the two of you with his towel. It wasn't very effective, but it was hot. Upon finishing, he just dropped the musky towel to the floor and the two of you kissed again.
Your dad quickly broke off from it and grabbed your hand, leading you into the bedroom. He released your hand as he climbed up onto the bed, then leaned his chest onto the mattress, using his big strong hands to spread his huge muscular glutes. You stared into them, seeing for the first time your dad's big bull sphincter in a jungle of dark hair. It twitched and winked at you, inviting you to dive right in.
"What are you doing, dad?" you asked him, still not taking your eyes off his fat donut.
"Well, I figured after you allowed me to plow your amazing ass, the least I can do is offer mine," he replied, grinning back at you.
You didn't need to be told twice. You climbed up onto the bed behind him shoved your face into his crack. He moaned as you licked and tonguefucked him with passion for several minutes. The smell was overwhelming, and the taste was a 10/10 IGN. Realizing you were about to be lost between his cowbuns forever, you forcibly raised yourself back up and gripped his sides, positioning your dick with his hole.
But then, you felt insufficient as you looked down at your member. Your dad deserved something better.
Taking a cue from your changes to him, you decided to give yourself an animalistic trait. You watched as your dick sucked into your body, leaving your balls behind. Gradually, the skin of your sack and around the hole where your dick was darkened. Your balls expanded in size, enlarging from golf balls to tennis balls to baseballs and finally to ripe prize-winning apples. You smiled as you watched them hang lowly between your legs. Then the skin around your literal dick-hole began to puff out as the skin finalized on a dark grey color. The hole expanded to twice the size it was before, even bigger.
Finally, the tip of something could be seen starting to peek out. As more of it slid out of your new sheathe, it revealed its true nature as the flared head of a horsecock. You were greatly excited as you watched more and more of it stretch out of you, witnessing your thick medial ring for the first time.
Eventually, your great cock finished growing, spearing out of your groin a fat 18 inches of stallion-breaking stud-meat.
As satisfied as you were with your new addition, you were a little worried it might hurt your dad, so you copied the change you made to your own asshole in the shower to your dad. Nothing visibly changed, but you knew it had taken effect.
Now you were ready. You lined your new fat flaring cock to your dad's waiting hole and pressed it into it. It slipped right in with a pop! making your dad grunt. You slowly pushed your hips further, driving your horsemeat deeper and deeper into his hot rectum until your crotch met your dad's cheeks. Holy fuck did it feel amazing.
"Don't be shy son," your dad said teasingly. Ironic, if not for the change you made to his sphincter a moment ago, he would probably be dead right now.
You slid your enormous dick out of him inch by inch until the flared head was stopped by the tightness of his ring, then used all your might to ram it back in as hard as you could. Your dad moaned out as your dick rammed his prostate, no longer in the teasing mood. As you settled into a rhythm you stared out across your dad's expansive muscular back, at his thick bulging traps and delts, at the back of his cow ears as they twitched with each sensation in his bowels.
Soon enough you were slamming into him with abandon, the two of you grunting in unison. Your dad actually blew his load first, spraying the bedsheets without requiring a reach-around like a seasoned buttslut.
The sight of your hulking powerful dad being so submissive to you sent you over the edge, and your yellowish horse cream spewed into his bowels, filling him up with your special foal-cocktail.
You pulled your dick out of him and collapsed onto the bed. You fucked him so hard you were exhausted.
Your dad was still on his hands and knees next to you and just laughed at your exhaustion, giving your thigh a playful couple slaps as your huge limp pillar of horse flesh shrunk and receded back into your sheathe.
"That was great son, thank you. I'm so proud my youngest is becoming such a stud," your dad said happily.
Your dad then climbed off the bed, some horse spunk still leaking out of his hole down his thigh, which he ignored.
"Alright, I'm headed to the gym," he announced. Apparently the workout you two just had wasn't really a workout for him at all.
He walked right past his dresser, disregarding the requirement for clothing.
"I'll probably be back in a couple hours." He reached the doorway to the hallway and stopped, turning to face you. He leaned his elbow against the doorframe and crossed one of his powerful legs behind him. God, he was such a hunk.
"That is, unless you cared to join me?" he added, smirking and eyeing you sexily.
You replied...