Batman: The Ultimate Evil themes concerning child sexual abuse and explored the topic of child sex tourism. The publisher required Vachss to follow certain rules, like making a clear distinction between fiction and reality and prohibiting the Batman character from killing, cursing, or having sex. In the story, billionaire Bruce Wayne, who as a child witnessed the murder of his parents Thomas and Martha, encounters the social worker Debra Kane, who takes Wayne to check up on her clients: he sees clear cases of child abuse and brave but futile resistance to it. Wayne's loyal butler, Alfred Pennyworth, gives him the secret files from
Batman: The Animated Series as the Mad Hatter, David Warner as Ra's al Ghul, Michael York as Count Vertigo, Kate Mulgrew as Red Claw, George Murdock as and George Dzundza as the Ventriloquist. One of the series' best-known inventions is the Joker's assistant, Harley Quinn, who became so popular that DC Comics later added her to mainstream Batman comic book continuity. The Penguin underwent change for the series; his appearance was remodeled after the version seen in "Batman Returns", which was in production simultaneously with the series' first season. New life was also given to lesser-known characters for the series such as the Clock