Ace Chemicals is first featured in "Deep Cover for Batman". It is still the place where the Joker is created but on a parallel earth, there was also known to be an Ace Chemical plant where the villain Owlman did exactly the same thing to the hero known as the Red Hood (an alternate Joker) who was using the chemical plant as a hideout; Owlman deliberately dropped the Hood into the vat of chemicals, creating the character's appearance, but keeping his sanity.