Jeff decided to go outside while he waited for the changes to take hold. He walked around his backyard, quietly taking in the warm sunlight and the fresh air. He wished he would never have to leave this beautiful world behind.
Just then, he felt a pain in his body, near his intestines. At first, he wasn't worried, since he had cramps like these every now and then and they usually passed after a minute or two. But this wasn't going away. Jeff unbuttoned his pants to try and relieve some pressure.
Then his feet started hurting, so he took his shoes off. And that's when he saw it: His feet, slowly bunching up into globs of flesh and then hardening into...hooves. Two great big black hooves. And his ass was growing and thickening, so much so that by the time Jeff tried to take his pants and underwear off, they ripped and he had to pull them off and toss them onto the grass. The pain forced him to the ground as his rear end bloated out, until his torso was nearly as long as the rest of his body. He watched as his tailbone suddenly burst out through his skin and two thin legs sprouted from his back and formed two additional hooves. When Jeff tried to get up, it took him nearly two minutes because his body now weighed as much as a standard-sized refrigerator.
When he did finally get up, the changes accelerated. Jeff's shirt was torn to shreds as his biceps and pecs began putting on layers of muscle. His arms beefed up until they looked like the ones in a old-time boxing poster. A six-pack adorned his chest. And Jeff felt his head growing in size as a thick mass of facial hair grew to cover his mouth and chin and his jawline became chiseled and hard
Finally, the changes stopped. Jeff took in his centaur's body, and noticed that in addition to his new horse tail and legs, he was now sporting an impressive horse cock, covered by a thick sheath. He began moving around the backyard, first by trotting and then by running, getting a feel for what it was like to move around on four legs. When he got hungry, he simply walked over to his neighbor's yard, pulled some fresh apples from a tree growing in the garden, and ate them, core and all.
Jeff felt incredible. He was strong, fast, and most importantly, well-endowed. But what now?