Actors Mark Hamill (Joker) and Kevin Conroy (Batman) have both played these characters for over 25 years. Both actors have repeatedly said that they were "retired" from voicing the characters. Hamill has said that while he enjoyed every minute of being the Joker, the years of voice work had put a huge strain on his voice and that someone else should have the opportunity to "don the psychopathic clown". Both Hamill and Conroy have stated that at their age the repetitive nature of the characters had become tiring. Both did say if there were ever a great story to reprise each character, they'd return. In addition to this series each returned for Batman: Arkham Knight and the animated film, Batman: The Killing Joke.
