"mmm... i don't know which one to choose" says Mary looking at the variety of vials. Closing her eyes she picks a vial (still thinking all the vials are about animals).
"Ok, here goes nothing" she though as she drank, an leaving it in its place. Not knowing what the changes will be she awaits for every tingling, stirring, pulling, thrusting, etc. sensation.
Then, there was a tingle in her crotch. Looking down, she sees her udder deflating, and her hooves disappearing, leaving only hairy? legs and the tail. She starts pondering about what vial she had used, right the the tingling sensation returned, this time as a pulling sensation in her clit, as this one was pulled along withe her ovaries, forming a penis and testicles.
"Oh my" was all she could say...