With Friday's reveal that the R-rated "Killing Joke" animated film includes a Batman/Batgirl sex scene, a lot of fans were shocked. Considering the typical nature of the duo's relationship in the comics, and the fact that it wasn't a part of the original graphic novel by Alan Moore and Brian Bolland, the filmmakers weren't surprised. Now that the secret's out, producer and DC Comics animation vet Bruce Timm has opened up about the controversial moment.

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"It came from a three-way conversation between [co-producer] Alan Burnett, [screenwriter] Brian Azzarello, and myself," Timm said of the scene's origins in an interview with Vulture. "I don't remember who initially came up with the idea, but we all kind of jumped on it all at the same time and said, Yeah, that's kind of where we need to go. My memory kind of says it was Brian, maybe, who came up with the idea. But I'm not sure."

Timm noted in the interview that he wasn't shocked at the reaction to the scene. "We were aware that it's a little risky. There's definitely some stuff in that first part of the movie that's going to be controversial. Here's where we came down on that specific issue: It was really important to us to show that both of the characters make some pretty big mistakes. I mean, his 'parental skills' aren't that great. Maybe never having had any kids of his own, he doesn't realize that if you tell a kid to not do something, they're going to want to do it even more. And then she makes some mistakes and then he kind of overreacts to her mistakes and then she overreacts to his overreaction. So it's very human; it's a very understandable story. It's tricky because it's messy, because relationships are sometimes messy. But to me and to Alan and Brian, it was all very fascinating to us to explore that angle."

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Asked what kind of reaction he was hoping for, Timm said, "I have no idea. I mean, I can kind of predict. Some people are going to be just freaking out, and some people might be going, 'Okay, I can see that kind of makes sense. It's not a comfortable place to be, but...We'll see.'"

"Batman: The Killing Joke" will be available for Digital HD download on July 26, and arrives on Blu-ray/DVD on August 2.