When Robert Downey Jr. first got the call about possibly starring in “Tropic Thunder,” the 2008 Hollywood parody helmed by actor-director Ben Stiller, the “Iron Man” lead was conflicted. Downey was slated to play the character of Kirk Lazarus, a five-time Oscar-winning Australian actor who undergoes “pigmentation alteration” surgery to portray a black soldier in the satirical film-within-a-film, and the job carried a major risk: wearing blackface makeup.

“I thought: ‘Yeah, I’ll do that. I’ll do that after ‘Iron Man,’ ” Downey, 54, said during a recent appearance on “The Joe Rogan Experience” podcast, recalling his conversation with Stiller. “And then I started thinking, ‘This is a terrible idea.’ ”

Downey’s hesitation was brief.

“I thought: ‘Hold on, dude. Get real here. Where is your heart?’ ” he said earlier this month. “My heart is a) I get to be black for a summer in my mind, so there’s something in it for me. The other thing is I get to hold up to nature the insane, self-involved hypocrisy of artists and what they think they’re allowed to do on occasion.”

“Tropic Thunder” received positive reviews for its scathing commentary on Hollywood, but also raised eyebrows with its blackface and drew criticism for its depiction of people with mental disabilities. The actor’s reflections on his decision to join the cast circulated widely Tuesday after IndieWire reported on the Jan. 15 podcast segment. By early Wednesday, the roughly 11-minute clip had been watched nearly 4.5 million times and garnered thousands of comments as fans praised Downey’s performance, which earned him an Oscar nomination in 2009.

“Ninety percent of my black friends were like, ‘Dude, that was great,’ ” Downey said.

Appearing on the show to promote his new film, “Dolittle,” Downey found himself looking back on “Tropic Thunder” after host Joe Rogan asked whether he thought the 2008 movie — replete with uses of a derogatory label associated with mentally disabled people — could be made today.

“Tropic Thunder,” which was released in August of that year, was described by The Washington Post’s Ann Hornaday as “a rude, crude, over-the-top satire about rude, crude, over-the-top action movies” with a “hall-of-mirrors sense of humor” sure to “effectively weed out the easily offended even before the movie — or, more accurately, the movie-within-the movie — gets started.” The movie maintains an 81 percent rating on Rotten Tomatoes, an online review aggregator.

The film stars Stiller, who also directed and co-wrote the script; Downey; and Jack Black, and it features a cameo from an almost unrecognizable Tom Cruise. In the flick, the actors are playing actors cast in a big-budget adaptation of a Vietnam War memoir, but things take a turn when their director (Steve Coogan) decides to drop them into a jungle with the hopes of sparking more authentic performances.

Downey told Rogan that his mother cautioned him against playing the part of Lazarus, a method actor who at one point in the movie says, “Man, I don’t drop character till I done the DVD commentary.”

“My mother was horrified,” Downey said, before slipping into an imitation of his mother. ” ‘Bobby, I’m telling you, I have a bad feeling about this.' I was like ‘Yeah, me too, mom.’ ”

But Downey’s decision paid off as he went on to receive nominations from the Oscars, the Golden Globes and the Screen Actors Guild Awards for his performance. In past interviews, Downey emphasized that his character differed from more egregious portrayals of blackface.

“At the end of the day, it’s always about how well you commit to the character,” he told Entertainment Weekly in 2008. “I dove in with both feet. If I didn’t feel it was morally sound, or that it would be easily misinterpreted that I’m just C. Thomas Howell in [the 1986-movie ‘Soul Man’], I would’ve stayed home.”

At the time, he credited “people who are high-minded enough to not be racist or offensive” for the film’s ability to toe such a fine line, Reuters reported.

On Rogan’s podcast this month, the actor reiterated his praise for the people behind the movie, namely Stiller.

“Ben, who is a masterful artist and director — probably the closest thing to a Charlie Chaplin that I’ve experienced in my lifetime,” said Downey, comparing Stiller to other film greats such as David Lean and Francis Ford Coppola. “… He knew exactly what the vision for this was. He executed it. It was impossible to not have it be an offensive nightmare of a movie.”

While Downey’s black friends may have told him his performance was acceptable, others did not share that view. A 2009 essay in the Root, an African American-oriented online magazine, criticized Downey’s Oscar nomination: “A century after D.W. Griffith’s ‘classic’ The Birth of A Nation, some white folks still think it’s OK to parade around in blackface. Hell, many feel empowered in the march to the post-racial America. Whoa Nellie! It’s not OK! It’s obnoxious, easy and pathetic.”

Addressing such critiques, Downey said: “I can’t disagree with them, but I know where my heart was. It’s never an excuse to do something that is out of place and not of its time, but to me it was just putting … a blasting cap on.”

Rogan noted that “Tropic Thunder” would probably be the last movie of its kind, citing recent controversies involving blackface that sparked fierce condemnation of public figures, including Canadian Prime Minister Justin Trudeau, who faced backlash last year after images surfaced of him appearing in brownface and blackface makeup when he was younger.

“It’s an interesting and necessary meditation on where is the pendulum. Why is the pendulum right?” Downey said. “… But again, there’s a morality clause here on this planet, and it’s a big price to pay. And I think having a moral psychology is job one, so sometimes you just got to go, ‘Yeah I effed up.’ Again, not in my defense, but ‘Tropic Thunder’ was about how wrong that is, so I take exception.”

The actor went on to stress how seriously he took the role, telling Rogan that he reviewed his lines “a thousand times” before shooting.

“It was a piece of work I was doing, and I cared about doing it as professionally and as honestly as I could,” he said.