Conroy said of that infamous final scene:

“Isn’t it crazy? I was really proud of that … because when you get into a scene like that, it’s not about making voices. It’s about really living the scene … you’re acting; voice acting is acting. And so Mark and I are in there together, and the madness that took over that room when we were both laughing so — and the laughing grew and grew, and then Batman’s laughter takes over. I was just really proud of it. I love that aspect of that. There’s a similar thing that happens at the end of Arkham Knight, the last of the games. It ends in a similar world psychologically for me as Batman. And I was just really proud of it.”

In the scene, Batman has beaten the Joker but offers him help. The Joker refuses but says it reminds him of a joke about two escaping asylum patients who try to jump from one roof to the next. The first one gets across, but the second is scared. The first says he’ll shine a flashlight between the building so the second can cross a beam and not fall. The second says, “What do you think I am, crazy? You’ll just turn it off when I’m halfway across.” The Joker laughs, and Batman joins him.

It’s chilling, and yet it’s clear that these two enemies cannot exist without the other. They cannot kill each other because, in the end, without Batman, the Joker ceases to exist fully, and vice versa. They’re a team, just as Conroy and Hamill were. There may have been madness in the booth, but it’s because the two actors worked so perfectly together and, as Conroy said, lived that scene.

“Batman: The Killing Joke” is streaming on HBO Max.