She will bring a knife out and sever your fingers. She will get a Chansey arm, out of a canopic jar, and than sever your whole arm, putting the fingers and the skin into the jar in which the Egg Pokemon's arm was inside. She will get medical sewing equipment out of a plastic bag, and sew the new arm onto the bloody stump where your human arm once was.
Shortly after, your new flipper-like arms will be controllable by your brain. Joy will gouge out your eyes, cut off your legs, and shove your head into a machine. That machine will deform your face to look like a Chansey's. She will take Chansey eyes out of another jar, and place them into your empty eye sockets. She will do the same for your other body parts.
You will wake up, and Nurse Joy will be cutting off the top of your new head. She will carefully take out your brain and place it in a canopic jar. She will take out a well-preserved Chansey's brain and put it in your head. She will slowly sew the top of your head back on.
You will wake up in a Pokeball, and will obey Nurse Joys every word. You will be a Chansey. Her Chansey.
I originally posted this on Google Docs eons ago, only it was originally a Pikachu instead of a Chansey. LINK: https://docs.google.com/document/d/1JUVlTE32Z1-LnXIaBISNcRW7oc7EJdSF_3PuidDs4AE/edit