18th Annual Critics' Choice Movie Awards - Backstage And AudienceBefore he donned the cape, Ben Affleck put up the bat signal to the men who've previously Batman, George Clooney and Christian Bale.

As he related on "Good Morning America," he received some sage words of advice from the two actors before embarking on filming "Batman v Superman: Dawn of Justice."

"I talked to Clooney and he gave me some advice which is not repeatable," Affleck said. "And I talked to Christian, who just told me to make sure I got a zipper in the suit, which was valuable, practical advice as it turned out."

Clooney played Batman in 1997's lamentable "Batman & Robin," while Bale crusaded in Christopher Nolan's trilogy of films: "Batman Begins," "The Dark Knight," and "The Dark Knight Rises."

Aside from seeking wisdom from his predecessors, Affleck had a more difficult task in preparing to play Batman -- getting in shape. Seeing co-star Henry Cavill's ripped physique in the first movie, "Man of Steel," was daunting.

"He has definitely set a high bar but he also has to be in that high bar because he's, you know, an alien," Affleck said. "I figured I had a lower bar to reach because I'm just a man after all, but I ended up putting on about 20 pounds of muscle, which is really hard to do in my advanced age."

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