The Tale of the Mystical Mirror - S5-E3
Question: When Laurel asks Vicky where Miss Valenti is and Vicky doesn't know, why does Laurel make a vomiting motion/gesture (pretending to stick her finger in her mouth)?
Answer: Maybe she just doesn't like Vicky.
Answer: Because he stole a chemical from his lab.
But Batman knew that with it, Clayface could permanently retain his shape and Clayface desperately wanted to be Matt Hagen again. In a sense, Batman stopped Clayface from becoming human.