Your ex-girlfriend-turned-anthro-cowgirl looks down at you sitting on the floor with wide eyes. "I think it's only fair that you experience what I did, but there's no way you're getting this lamp back. You're mine! Genie, I wish for you to make this sorry excuse into a fat female cow!"
"No!" You shriek and the burning ashes from the genie's cigar drop down on you. You are wracked with a sudden convulsion, forcing you to curl up in a ball. Then, just as quick, you arch your back. You gain pounds quickly, filling up your clothing. With a ripping sound, they give way. You don't care that you're suddenly naked, you can only think about becoming a cow!
Course bristles begin their growth. White with black spots. You hold yourself up on your hands and knees. You keep porking up, swelling to your new large size. Your manhood shrinks within you and a warm sensation spreads over your lower belly. Your udder. It balloons with milk. You let out an uncontrollable moo in protest.
The cowgirl watches with glee at your discomfort. She revels in it. You keep changing, your arms and legs snap into the correct configuration even as hooves begin forming.
Your nose swells and your face pushes out just as a tufted tail springs out behind you.
Taking a couple of shaking steps, you finally finish transforming. You moo at the cowgirl towering over you. Partly because you aren't liking this and part to have someone milk you before you burst!