Batman an occasional ally and romantic interest), the Penguin, Ra's al Ghul, Two-Face, the Riddler, the Scarecrow, Mr. Freeze, Poison Ivy, Harley Quinn, Bane, Clayface, and Killer Croc among others. Many of Batman's adversaries are often psychiatric patients at Arkham Asylum. Batman's butler, Alfred Pennyworth, first appeared in "Batman" #16 (1943). He serves as Bruce Wayne's loyal father figure and is one of the few persons to know his secret identity. Alfred raised Bruce after his parents' death and knows him on a very personal level. He is sometimes portrayed as a sidekick to Batman and the only other resident of
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