Jeff was reading the description of the possible changes, and noticed that it said that this change would replace the body part of another person than the user. He didn't realize that it meant by turning the user into it, though...
"Hey, I could help my uncle Bill!"
He said, a smile spreading across his face. Jeff has always looked up to his uncle Bill, and was very close to the old man. He had lost a leg in the war, however, and Jeff thought that this program could help him fix that.
He clicked through the options. Change over the course of a few minutes, and give him time to get there first; he wanted to see his uncle surprised by the new gift. Mental change? It must mean for his uncle. No, he wanted him to know what had happened. Reality change...sure, his uncle would have had a happier life with a leg, though he would leave it so he remained aware of the change. Duration? Well, he wouldn't want his uncle to go back to having only one leg...
With a large smile, Jeff clicked "Permanent and Irreversible", and as he clicked 'Begin', his fate was sealed.
He picked up his bad and headed out the door, a spring in his step as he pictured how happy his uncle would be. As he travelled, his skin tingled and he was feeling hot and flushed. Something strange was coming over him; he kept thinking about his uncle, about how he needed to get close to the older man. Closer than ever.
When he got to the house, he knocked with a huge blush. After an agonizing pause, the door opened, and Jeff's face split into a huge grin as he saw Bill.
Uncle Bill was a large man, over a foot taller than Jeff, and heavy set with it. His large round belly was as hard as a barrel, and under his fat was a tough layer of powerful muscle. The older man had a short-cropped salt-and-pepper beard and buzz cut, and his handsome fat was set in a masculine smile.
Jeff couldn't help but look down, and see his uncle's left foot, where he was balanced carefully on a prosthetic limb. He felt strange urges overcome him, and reached down to stroke his uncle's leg through the denim of his jeans.
"Jeff my boy, what are you...doing..."
His uncle's gruff voice trailed off as a tingle of electricity ran between them both. Silently, he followed the older man indoors, and watched him sit down on the couch, a slightly faraway smile on his bearded face. Jeff began peeling off his clothes, tossing them aside until he was standing naked in front of his uncle. Then he reached forward, taking hold of his uncle's best and pulling it up wards, throwing it on the floor and stroking his hairy, bristly chest.
He slid onto his knees, unwinding the tough laces on his uncle's black boot, before holding it and sliding it off, stroking the slightly damp, musky sock underneath. He peeled the sock down, letting it fall in a ball to the carpet as he gently stroked and kissed his uncle's hairy, muscular foot.
Jeff's eyes had glazed over with the feeling consuming him, and he reached up and unbuttoned Bill's jeans, holding them and pulling them slowly down, revealing his uncle's hairy muscular legs, and his musky, slightly damp, tight briefs. A hard, throbbing lump was visible in the white cloth, and Bill slowly reached down, hooking his thumbs under the waistband and sliding them down, tossing them aside, and sitting naked in front of his nephew.
Jeff gazed in awe at his uncle's naked body, desperate to get close to it, to become a part of it. His hands trembled, and he reached over to the plastic fake leg, unbuckling it piece by piece, and letting it drop to the ground, showing the stump where Bill's leg was lost so long ago.
Jeff turned around, pushing his ass in the air as his uncle slowly rose from the couch, lifted his truncated leg, and pushed it down, pressing it against Jeff's ass. Jeff felt something entering him, a feeling of pressure and strength running through his body. The flesh in his ass rippled and began to flow onto his uncle's limb. Jeff's legs rose in the air, pressing against Bill's thigh, shrinking and melting into the muscle. Jeff could feel the power of his uncle's leg above him, as if it was a part of his body. He groaned as his uncle's blood began pumping through his body, changing him. He pressed his face against the ground as his body cracked and shifted, changing shape. He looked to his left, watching as his arm shrank into his body, pulling in shorter as his hand fused into one lump, and a large square nail formed on the top as his fingers melted away. Meanwhile, his right arm shrank even more into his body, his hand fusing into three more round, strong toes.
He felt his chest push into the carpet, the skin becoming tougher as it reformed into the sole of his uncle's new foot. His head began to shrink, the details fading as it became smaller and rounder, and his hair fell out in clumps, being replaced by the hard clear material of a toenail.
Bill was panting and groaning as his nephew wriggled and pressed against his leg. He reached down, grabbing tightly hold of his thick, powerful cock, stroking the foreskin up and down slowly, grunting as pleasure trickled through his body from head to toe, through even the body of his nephew as it cracked and reformed.
He looked down in a haze of lust, watching as Jeff slowly changed into the form of a new foot. The pleasure began to peak as he watched body hair sprout over the strong new limb, and with a roar, his dick exploded with cum, spraying his belly with creamy semen as he stretched his toes, clenching both his feet tightly, reveling in the feeling of being whole.
They both sat there for several minutes, Jeff's mind blown with the strange feelings in his body, unable to control any part of himself. Eventually, Bill stood up, and Jeff felt his face and chest pressed into the carpet, and stamped up and down. He was now Bill's foot, forever.