Transcript for Hugh Jackman calls 'The Greatest Showman' a 'passion project'
Reporter: Wolverine is trading in x-men claws -- ??? tell me do you want to go ??? Reporter: For tophat and cane. The ever-versatile leading man Hugh Jackman depicting a decidedly more human hero. P.T. Barnum. No one ever made a difference by being like everyone else. Reporter: In "The greatest show man." As a ring master you have a cane, a hat. Nice flair. I like the panache. Put the hat on the head. Oh, come on. Reporter: With those tricks nobody's better than Jackman for the role. I had to do it with my eyes closed. That's incredible. There you go. I'm showing off now. So we had ten weeks of rehearsal that I was vocally preparing for two years before. And I literally came straight from shooting "Logan" to shooting this. I had a weekend off, then I came to it. I can tell you, this was tougher physically. What do wolverine and P.T. Barnum, if anything, have in common? They have some things in common. On the surface, very different people. But they both have fight. Push them up against a wall, back them into a corner, look out. And I've got a little bit of that. Reporter: The movie an over-the-top homage to the father of show biz. A musical take on the real life of pt Barnum. The risk-take history founded the Barnum & Bailey circus in the 19th century. Seven years in development? And a half. And a half? Not that anyone's counting. What's it like after all those years to see it come to life? It's a great thrill. It's nerve-racking because I care so much about it. We have become a family. Also I've been around long enough to know these things don't come along very often. I think I've had an idea -- Reporter: The film follows his journey in creating the first-ever circus. Putting together a show. I need a star. Reporter: Rallying a group of outcasts and misfits into a spectacle. United against backlash and bigotry. There is a strong current of taking outcasts, allowing them to come out of the shadows. Yet at the same time it's met with some of sort of mob mentality. Right. Are there sort of parallels in current affairs that you draw on? Absolutely. Because art always reflects life. As we develop this for seven years, the theme of inclusion, the theme of tolerance, came further and further to the surface of the movie. I'm an Australian. I've come all the way across the world to America to live here. And I have only ever felt welcomed. Supported. And I just have a feeling now, we're just retreating a little bit. Reporter: The film's glowing depiction of Barnum's life makes some selective jumps. Glancing over accusations that he took advantage of, even exploited, people who were social pariahs. P.T. Barnum is a bit of a flawed hero in real life. Yeah, he's definitely a flawed character. I think that's why I was drawn to him. Was he probably using the bearded lady and Tom thumb in the beginning to sell tickets? Yeah. He was. But what happened was, he genuinely created this family. I'm not sure if that's what he intended in the beginning. Reporter: Barnum's famed circus closed its doors for good earlier this year amid dwindling ticket sales. After years of animal cruelty allegations by rights groups. In the movie you ride a cgi elephant. Yes. Was that fear of the cruelty to animals accusations? We were never going to use animals in the movie. Everyone in the film totally agrees animals should not be used in circus or form of entertainment in that way. That's a bygone era. This is 1850. It is there and that's why we used cgi animals because we don't want anyone to think we were exploiting or celebrating that in any way. Reporter: Barnum may have invented showbiz, Hugh Jackman is now dominating it. A rare action hero headlining blockbusters like x-men. ??? Who am I ??? Reporter: Then morphing. From superhero to song and dance man. Jean belle Jean in "Les miserables." Hugh Jackman! Reporter: Charming enough to host the oscars. I'm an Australian who played an Australian in a movie called "Australia." Reporter: And the tonys. Not once but four times. ??? I love the tonys ??? Reporter: Plus he took one home. Hugh Jackman. Reporter: The film and Jackman's portrayal of Barnum already nominated for golden globes. A role far different than the one that made him a household name. Wolverine. That character's final performance hit the screens earlier this year in "Logan." You watched that final performance with tears in your eyes. Oh, yeah. Not just in my eyes. Rolling down my cheeks. I'll be honest. I was so nervous to see that final showing. And I just really was pinching myself and felt so blessed and so relieved. Because I knew it was my last. And I wanted to go to sleep at night for the rest of my life knowing that I'd made the movie that I'd always felt was there. Reporter: In this film Jackman joined by a powerhouse cast. Michelle Williams as his ever-patient wife. Zac Efron as his junior partner. ??? What percentage of the show would I be taking ??? You talk about transcending class in this movie. In some ways Barnum, the story of Barnum is the story of the birth of show business, but I would go further and say it's the story of modern America. In the beginning there were limitations of your class, of your background, of the family name. There were certain places you couldn't go. Barnum was one of those. Reporter: A big-budget Hollywood musical still not a sure thing, even when the composers are the Oscar and tony-winning duo behind "La la land" and "Dear Evan Hansen." ??? City of stars are you shining just for me ??? You had two songwriters who at the time were somewhat unknown. Yeah, they were unknown. They were unknown. You had to even fib some credentials in order to get the studio to buy in? May have been some Barnum hoodwinking going on. These young guys got in there, met Michael Gracie, our director, wrote one song we loved. When was when was the hook? It was a million dreams. It was a beautiful, simple song. ??? Every night I lie in bed the brightest colors fill my head ??? ??? a million dreams are keeping me awake ??? It was a hook. Mark Gracie went in had a meeting with the studio exec, I won't tell you the name. The exec is like, who is these guys? Justin and Ben? Oh, they're very big, they just won a Tony. For what? "James and the giant peach," the first thing that came to his mind. There's never been a Broadway production of "James and the giant peach." Now they just got nominated for three grammys, they won the Tony, they won the Oscar for "La la land," and they don't talk to me anymore. They won't return your calls. It's fine. Reporter: For "Nightline" I'm juju Chang in New York. Our thanks to juju. The greatest show hits theaters it's a plane, it's an unidentified
This transcript has been automatically generated and may not be 100% accurate.