Your mind races. If your butt has already gotten too big for your pants, the rest of you won;t fit in your clothes much longer, either. You scramble to undo your shoes and kick them off just as they start to swell out, and yank pants and shorts down and off completely. Then you get your shirt off, and stand naked in the room.
Then you feel a burning in your crotch. Looking down, you see that the sweep of black hide has reached your groin, and things are getting very interesting. Your privates are becoming rather public, doubling, then tripling in size as they turn black and heavy. A thick sheath of flesh forms around the base and works up the 4-inch wide horse cock, pulling it against your belly.
Balance is off, and it's easy to see why. You are now standing on large hooves - from the waist down you are completely equine. However, the horse parts keep getting larger, and the black hide sweeps up your belly and back. It looks like you are going to be a real neigh-sayer if you can't stop the transformation!