Cranston's character, Mack, is the ringmaster of The Big Top Mall Show, starring Ivan -- a giant gorilla ripped from his family as a baby.
Mack is Ivan's friend and caretaker, but he's also ready to exploit him when he discovers his talent.
"I like the complexity of Mack because he's a man struggling, he's a man who's fragile in some ways, and there's a vulnerability to him," Cranston said.
There are about 10 animals in the movie, and none of them were real, he said. They were all computer graphics.
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"There were men in green suits who were pushing around a huge metal cart with wheels on it that would become the big elephant, or a man in a green suit with a puppet for the dog," Cranston said.
His professional training helped Cranston get past the "men in green suits" and into his character.
"We're actors and the first acting classes you ever take are all about allowing your imagination to not only exist but thrive -- let it come in, let it go, let it explore," he said.
"The One and Only Ivan" starts streaming Friday on Disney Plus.
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