Before Sean could reply, he felt started to feel strange. He felt a warm pulsing begin in his chest and felt his heart begin to beat faster. He couldn't tell if it was from excitement or the change, but he figured it was probably a bit of both.
Sean felt his chest start to push outwards with each thump of his heart. The warmth building pleasurably with each pulse. He felt the muscles in his chest shifting and pulling as they expanded and his bones slowly reformed. Sean looked down to see his chest beginning to gain muscular definition beneath his shirt which was slowly tightening as he bulked up.
As his chest began to expand, he felt the warmth spread outwards. First it moved down into his stomach, which began to tighten with muscle as well. The slight belly he had was slowly melting away to reveal a tight and toned 6-pack underneath - the definition of which was now clearly visible through the t-shirt Sean was wearing.
At the same time the warmth moved across Sean's back and down his arms and legs, which began to pulse muscle along with the rest of his body. Melting away his slight amount of flab and replacing it with hard, toned muscle.
Sean began to feel his clothes tightening as he bulked up, he watched in awe as his arms and legs tightened and grew, giving the odd flex and watching as the muscles, previously hidden, leapt forth and shifted beneath his skin. As his muscles grew, Sean could feel as well as see the power building in his body. He was unable to keep from grinning like an idiot as his dreams came true.
Next the changes began on his skin. Sean felt as if someone were running their fingertips lightly along his entire body, teasing each bump and crevice on his changing form with the slightest of touches. He was dimly aware of a feeling of his skin drying out and toughening, and watched in fascination as all the hair on his body seemingly slipped out of its folicles in an instance. As his skin changed to thick hide, he watched it change color. His stomach paled to a yellowish brown, as the backs of his hands and feet, and indeed his whole body, darkened to a deep brownish red.
Sean was jarred out of his trance by the now painfull tightness of his clothes, and a numbness in his hands and feet. He felt as if his clothes were being stretched to their limits by his muscular frame, but still he grew on. He grinned wildly as his shirt began to rip from the stress of his shifting bulk - each tear revealing more thick dark hide underneath. "My hide", he thought to himself, "my goddamned HIDE!" His skin now had the look of weathered leather, and Sean doubted that even a knife could peirce it. He began to run his hands along his chest, helping to tear away his tattered shirt as he grew, so that he could feel the texture of his rough pebbly skin under his fingertips.
Then Sean caught a look at his hands, which were now pulsing with the same gentle warmth as the rest of his body. He watched as the first and second fingers, and pinky and ring fingers pulled together - unable to move independently. He felt as if someone were massaging his hand, and could see the bones shifting and snapping under the skin as his hands fused into three-fingered digits. As the nails on his fingers merged they seemed the thicken and grow, fusing into great claws at the tips of his fingers. They looked sharp and strong, and as he flexed his new hands he imagined he could crush just about anything with his powerfull new mitts.
His legs were next. As the warmth filled them he vaugely felt his feet shifting in his shoes, which began to bulge obscenely from the changes within. He grinned again as his legs and feet grew stronger, splitting his pants up the side. His feet began to tear through his shoes, and three great toes tipped with large claws emerged. Sean watched as his feet grew and grew, adopting a splayed W position under each pillar of a leg. He flexed his new toes and watched as his new claws scratched great gouges in the floorboards. Sean was forced to stand on the balls of his feet as his heels grew upwards, making him stand even taller than he already was. It felt natural to him though, and he imagined with his new leg configuration and musculature he could run incredibly fast and far.
Simultaneously Sean felt a tingle in his head and his lower back. He felt his neck filling out, but also lengthening, at the same time he felt a pulling sensation from his tailbone. He stumbled a bit as his hips shifted, causing him to stomp one great foot on the floor, a great *thump* telling of the power contained therin. Sean felt his toungue and face go numb as he tried to watch everything at once, he had a vague sensation of his nose blowing up and expanding, as his viewpoint shifted. He knew his muzzle must be growing in, splitting his vision a bit. He grinned, and was surprised when he felt his lips pulling back from a muzzle he didn't realize he had, revealing teeth that had shifted into great daggers in his mouth. He ran his tongue along his new lips, feeling the tips of his (many) sharp teeth, amazed at its dexterity. He was amazed as well when he caught sight of it in his new eyes, creeping along the edge of his muzzle - he imagined it must be incredibly long and dexterous to live in such a dangerous mouth. This just caused him to grin even larger, his new teeth and T-rex visage making him look extremely menacing.
Sean was so enthralled with the changes to his face, he was surprise to feel himself tap the wall behind him - with a part of his body he'd never felt before. He quickly swung his huge predatory head around, much further than he'd been able to previously, and took in the sight of his new tail. It was thick and powerfull, muscles bunched along it from the point it left his backside to its tip making it look more like a python than anything. It wasn't as dexterous as he'd imagined though, and it swayed stiffly behind him when he shifted his weight, moving automatically to counterbalance his huge upper-body.
Sean felt the warm pusing draining from his limbs, leaving a feeling of crisp power in his hands, feet and tail. His head too began to cool as he inhaled deeply, taking into his huge new nasal cavity millions of new smells that threatened to overpower him by their sheer number alone. He was distracted from his newfound power of smell however by the warmth returning to his belly, moving dowards and growing hot.
Sean grinned maniacly, recalling that he'd opted to increase his sexual prowress as well. He could feel the warmth of the transformation pushing into his groin and begining to pulse...