Adam couldn't believe that his dad had just downed the entire potion! He walked over to the counter and picked up the stone flask his father had just drained. Adam's shoulders slumped and he sadly put the cork back in, now that it was empty. He had been curious about what the strange liquid might be.
"You should work out with me," Dad said, interrupting the disappointment Adam was feeling. "It's only been a few weeks, but I swear I can feel some progress!"
Adam turned to look at his dad, who was standing in front of the TV, watching the oiled-up musclemen on it. His father brought up his arms and flexed. Surprisingly respectable biceps rose under his skin, pushing up the sleeves of his tee shirt. Higher and higher the muscle rose, getting bigger and rounder the longer his father flexed. Adam nearly choked on his own tongue as he realized his father was growing all over! Big, firm muscles filled the shirt to the brim, stretching it across thick, beefy slabs of brawn. His father's pants were likewise tightening around meaty thighs and impressive calves.
"Oh fuck..." Adam finally breathed, hardly able to believe what he was seeing. Adam was unfamiliar with the magical properties of the flask, just as the shop owner had been. But right then, seeing his father turn into a hulking bodybuilder right in front of his eyes... Adam knew something was up. He looked down at the stone flask in his hand, and pulled off the cork. It was full again. His eyes widened. This... this must have been responsible... Yet he still didn't know how it worked. (And he didn't know that in the absence of any external ingredient to guide the transformation, the elixir latched onto whatever the drinker thought about becoming--in his father's case, a huge bodybuilder.)
Adam looked up at his father, eyes wide. His dad was big, strong, and dammit, hot as hell now! It made Adam's dick stir in his pants. He knew that he shouldn't be turned on, and he tried to look away. But out of the corner of his eye he saw his dad slowly pull off his shirt, revealing his bare, muscled torso. Adam's eyes locked back on, taking in the contours of muscle that rose under the skin. A moment later his father pulled off his pants as well, kicking them aside after stepping out of them, wearing only a pair of tight briefs that left nothing to the imagination--not the round, bubbled glutes that pushed out the back of the undergarment, nor the hefty package that dragged down the pouch in front of it. Adam's dick became fully hard as he ogled the magnificent specimen his father had become.