You continue to feel pain in your pants, as your own butt grows larger. Your own testicles swell up, as they increase their size, while becoming pink, along with the rest of your penis, as it extends, until it reaches the middle of your torso. Not only that, but you feel something growing out of the top of your butt.
You feel your butthole pucker as you lay down on the sidewalk on all fours, and feel white fur begin to form from your own butt. Your penis starts spilling out precum as you lay there struggling, while changing. You feel whatever was coming out of your butt, extend, while you lay there, and spill more precum from your penis, that has now had the shaft changed to look more equine. You turn to see what was growing out of your butt, and find that it was a tail, the same color as your head of hair.