You could feel your own feet begin to change, as the white fur that was on your butt started to spread, reaching the legs, which caused the feet of them to get longer, until the toenails began to turn black, and harden. The same thing was happening to your friend's feet, as he was trying to struggle, and get up from the ground.
When you looked back, you noticed that your own hands were growing as well, while your fingers began to extend even more than your feet did, as you noticed that they were beginning to fuse, while your nails became hooves on each hand. You look back at your feet, after watching your hands, and saw that your toes have fused into hooves as well. Just then, you gazed upon your friend's butthole, and noticed that it puckered, while your face began to extend, so you began to lick it.