You keep rubbing yourself, even though a part of your mind knows that it will only continue your transformation. You stop your stimulation when you see something in the mirror. You're starting to grow horns! Pointed, black horns start to push out of your skull. You raise your hands to feel them. A touch confirms that they are real. You also see that the hair is spreading down along your shoulders and arms from your chest and back. The hair doesn't look like normal body hair anymore, it's becoming more coarse, like animal fur.
Your previous change gave you more muscles in addition to hair on your torso and a beard, you wonder which animal has both these attributes and horns. A bison pops into your mind. You're turning into a half-bison! Your feet start to hurt, it's like your toenails are being crushed! You look down and find that your toes have fused so that your feet now end in black cloven hooves. Another pain sweeps up your legs, forcing you to now stand on those hooves and hold your heels in the air. The skin on the palm of your hands turns to black hide as your fingernails thicken and darken as well. You look back into the mirror as the mother of all headaches hits you. The agony is such that you collapse to the floor.
You get up once the pain subsides. You take another look in the the mirror to see a very bovine head on your shoulders. A head with curved horns and a beard. Standing brings discomfort to your lower back. You want to both see what's causing this feeling as well as getting rid of the cursed overalls. Now nude, you can see the totality of the change.
The discomfort was caused by your tail, long and topped with a tuft of fur. Your chest and upper back are covered in a thick layer of dark brown fur. A layer of shorter, brown fur covers the rest of your powerful new body. Remembering how you started changing, you turn so you can see your crotch reflected in the mirror. Your manhood now hands thick and low in front of beefy balls.
Your change is complete and you can hear the door unlock with a loud click.