Fallon perfectly segued a cute Affleck family story into Bat talk when he asked what his kids think of their dad playing a superhero.
"Every kid should see their dad as a superhero," said Affleck. "It's so awesome. I'm so excited."
But not everyone shares Affleck's enthusiasm. In fact, most don't. A petition even surfaced online demanding he be replaced from the film.
During the interview, the Oscar winner lightheartedly explained that producer Zack Snyder sent him online reactions to actors who were previously cast as the Caped Crusader -- a way to prepare him for what was expected to come.
"They sent me people who were in these movies who did a great job," he said. "These things were like, 'Kill him!' It was amazing."
Affleck added that he isn't fazed by the negative reactions, saying, "If I can handle the Emmy snub, I can handle anything."
The new Superman-Batman mash-up film will begin production in 2014 with a tentative release date of July 17, 2015.