Thanks to Andrea Romano, Kevin Conroy and Mark Hamill recorded almost all their dialogue together, allowing them to play off one another and enhance their overall performances. The voice director was incredibly actor-friendly and knew getting the two stars together would work for the show, leading to Conroy and Hamill developing a rule that they had to be in the same room for recording sessions. It’s not surprising then, that once Conroy passed, Hamill seemed to suggest he wouldn’t be getting in the booth as Joker again, telling Empire (via ScreenRant): “We were like partners. We were like Laurel and Hardy. Without Kevin there, there doesn’t seem to be a Batman for me.”
And it seems Conroy was equally enamored with his co-star. As he told The World’s Finest: “That Batman/Joker relationship, it’s almost like Joker defines Batman and Batman defines Joker. It’s the dark and the light. Sometimes it feels like either of us wouldn’t exist completely without the other. And Mark and I work so well together.”
But Conroy appreciated more than Hamill’s ability to enhance his own performance. Specifically, he was impressed by the way in which his co-star would embody The Joker during recording sessions — likening him to Jim Carrey and his animated presence. He continued:
“Mark becomes the Joker. I wish the audience could see him in the booth. His face is like rubber, and it’s like Jim Carrey, you know, he just becomes the character. And he’s, like, devouring the microphone. And when I’m doing Batman I get very kind of dark and broody, you know? It’s weird how we both inhabit the characters while in the room. It’s kind of fun.”
