"Don't think so, no", the bear however replied. "I like my cock as it is. I was more interested in the power of your cum... I suppose the same is true for me, right?".
"Of course", the clerk dutifully replied. Behind his back Derek and Jake, intoxicated by the idea of being werehorses, had started making out passionately on the couch. "Whoever tastes your sperm is bound to become big and furry, not to mention bald".
The colossus smirked. "Great. And you have to fully satisfy your customers".
The other man nodded, without showing an inch of hesitation. "As I said, it's my job".
"Perfect. See the spunk on that mirror? I want you to lick it clean while I fuck your ass bareback. How does it sound?".
The clerk's grin just went wide, showing his perfectly white teeth in all their glory. "I'd say I can't wait to help you with that, dear customer". He positioned himself doggy-style, offering his proud, tight ass to the bear, his tongue already busy licking the white goo splattered on the mirror.
The bear nodded approvingly... and then impaled the clerk with his 12 inches uncut sausage in a single, violent thrust. The suited man didn't budge nor yelp, but kept lapping the mirror like his whole life depended on it. "Good. Take it like a real man", the bear growled, pounding the ass roughly. "Is my cream starting to change ya? I'm sure you'll be hot as hell with some meat on them bones...".
Indeed the clerk was already looking a little bigger, his beard a shade darker, his hairline slowly but surely receding. His horsecock was dripping clear precum on the floor, like a running tap. "Unfortunately, this sperm has been outside of your body for too long, and it's starting to lose its power. Without a fresh supply, the majority of the changes will not happen", the clerk was devoted to his duty even while being violated anally and on the verge of transforming into a bald bear.
"Don't worry, cub, the 'fresh supply' is on its way". The man then looked at Derek and Jake, who had in the meantime gotten hard again and were sixtynine-ing on the leather couch. "You guys want some, too? I have enough spunk in my balls for a dozen guys". The two skaters stop sucking each other just so they could shake their heads.
"Heh, whatever", the bear thought, resuming his assault to the clerk's ass. "You're clearly not ready to become real men anyway. You're just two faggy cocksuckers who think they're hot shit just because they have big dicks". The aggressiveness and arrogance of a daddy bear have been slowly but surely creeped in a brain that less than ten minutes ago belonged to a shy, awkward teenager with an overwhelming attraction for big, mature men. The feeling of power, not only his own but also the one contained in his sperm, was more than enough to make him finally reach orgasm and coat the interior of the clerk's anus with creamy white fluid, quickly to be absorbed by his body.
The colossus dislogded himself from the other man's pucker and helped him get back on his feet. "I want to see you change", he declared. "My cum is turning you into a better man... And I can't wait to feel your gut pressed against mine".
The clerk's only answer was a long moan that became progressively deeper: he was lost in the ecstasy of changes, and could feel his pecs swelling and enlarging, his tight abs becoming a prominent muscle gut. His cheeks - and the majority of his body - were now covered in a thick layer of chestnut hair, with the subtlest hint of grey here and there. He put a joyous, contented smile on his face when he felt the blond mane of his former self falling from his scalp, leaving a smooth, bald head behind. Finally, as a last touch, his eyes turned a deep forest green, benevolent yet enticing. Curiously, the suit and shirt had morphed alongside him, and were still a perfect fit; his horse cock, however, didn't change, and looked more natural and not so freakishly huge like before.
The daddy bear was clearly appreciative of this. "You know what? I may have changed my mind about your cock..."