Tom Hanks Says Working with Son Truman on A Man Called Otto Is 'Special': 'I Changed His Diapers'

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Jeff Spicer/Getty Tom Hanks and son Truman Hanks

Tom Hanks has quite the history with his latest film costar.

Truman Hanks, 27, plays a younger version of his dad's crotchety character in A Man Called Otto, which will be widely released Jan. 13 and is based on Fredrik Backman's 2012 novel A Man Called Ove.

During a post-screening Q&A for the film on Monday night, Tom told PEOPLE what it was like working with his son, whom he shares with wife Rita Wilson.

"Without a doubt, it's special because, you know, I changed his diapers," said Tom. "But you get past that right away because you gotta show up, and you gotta hit the marks, and you gotta do it on time, and you gotta be right there."

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He continued of Truman, "I know what that takes, and he does too. It's a little different when it's the whole shebang. He was cast for a very specific reason. We resemble each other, he's not a stranger, and he knows what the pressure is, and he's gotta do it."

Tom, 66, also opened up about the realities of being an actor and feeling uncertain about his performance.

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"The thing that we both know is ... you don't know if you did a good job," he told PEOPLE. "All you can do is wait for that very surrealistic moment when you see the movie, and it's like, 'There it is.' It's gonna last forever. Even then, I don't think you have an idea of whether it works or not."

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P. Lehman / Barcroft Media via Getty (from left to right) Samantha Bryant and husband Colin Hanks; Tom Hanks and wife Rita Wilson; Chet Hanks, Elizabeth Hanks and Truman Hanks

Asked by PEOPLE what his experience was like working his father, Truman joked that he and his siblings have mastered the art of imitating the star. Tom also shares Colin Hanks, 45, and Elizabeth Hanks, 40, with late ex-wife Samantha Lewes, as well as Chet Hanks, 32, with Wilson.

"Whenever I do my imitation of him, people are like, 'That's not what he sounds like.' But I have to convey to you the way I hear him. Everyone else hears, 'Houston we have a problem'; I hear this grumpy old man who's mad at the DVD player," said Truman.

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Earlier this month, Tom weighed in on the nepotism in Hollywood conversation. He spoke with Reuters, per The Sun, about his role in A Man Called Otto and the "family business" of entertainment.

"This is what we've been doing forever," said Tom. "It's what all of our kids grew up in. We have four kids — they're all very creative, they're all involved in some brand of storytelling."

"And if we were a plumbing-supply business or if we ran the florist shop down the street, the whole family would be putting in time at some point, even if it was just inventory at the end of the year," the actor added.

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"The thing that doesn't change no matter what happens, no matter what your last name is, is whether it works or not," he said, referring to his family's respective projects.

"That's the issue anytime any of us go off and try to tell a fresh story, or create something that has a beginning, middle and end," the Forrest Gump star said. "Doesn't matter what our last names are. We have to do the work in order to make that a true and authentic experience for the audience."

"And that's a much bigger task than worrying about whether anybody's going to try to scathe us or not," he concluded.