Before your eyes, you can see your hair turning grey. You can see and feel your ears start to elongate. A strange pressure builds near your mouth and nose, so it doesn't surprise you too much when you see it begining to form out into a muzzle. Your front teeth are getting longer, and you can feel a tail begining to form in your bants. Your feet are getting darker and harder, but your hands remain more or less human. Your penis, however, has never felt better. Or bigger. You anxiously rub it through your pants, its full and long body is now extremely receptive to you. You finally relaese the building pressure as the transformation finishes. You let out a donkey's bray - full and wonderful. Your mind is a bit clouded by the sensations, but you know that you'd never want to go back to just being a human again.
After taking time to look in the mirror, you decide that the overalls are overkill. You take them off and get a good look at your new body. It is covered in fur, muscular, and great-looking. Your penis is still half erect.
You have a strange urge to do something.