Terror.

Not only did they both initially feel overwhelmed by the daunting responsibility of portraying the iconic civil rights leaders but they also felt their performances would likely be compared to those of others. Denzel Washington portrayed Malcolm X in the eponymous 1992 film that earned him an Oscar nomination, Samuel L. Jackson starred as King in Katori Hall’s Broadway production of “The Mountaintop” and James Earl Jones also portrayed King in the miniseries “Freedom to Speak.”

But with the support of friends and producers, Harrison and Pierre eventually overcame their doubts, delivering distinctive and bold portraits of the two men.

“MLK/X” is the fourth season of “Genius,” a biographical anthology series that has focused on Albert Einstein, Pablo Picasso and Aretha Franklin in previous installments. The final two episodes of the eight-part season, which premiered Feb. 1, run Thursday on National Geographic and stream the following day on Hulu and Disney+.

Co-starring as King’s wife, Coretta Scott King, is Weruche Opia (HBO’s “I May Destroy You”), and Jayme Lawson (“Till”) plays Betty Shabazz, the wife of Malcolm X. The executive producing team includes Gina Prince-Bythewood, Reggie Rock Bythewood, Brian Grazer and Ron Howard.

Harrison (“Chevalier”) and Pierre (“Foe”) knew each other — they are both involved in the upcoming “The Lion King” prequel, “The Lion King: Mufasa.” Pierre plays the title character, while Harrison plays the villain Scar.

Even though they share only a few scenes in “Genius,” they clearly became bonded during the project and expressed a palpable fondness for each other during a recent joint interview at a Pasadena hotel. Pierre occasionally patted Harrison’s knee during the discussion, calling him “my best friend.” This conversation has been edited for length and clarity.

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1. Aaron Pierre plays Malcolm X. 2. Kelvin Harrison Jr. plays the Rev. Martin Luther King Jr. (Christina House / Los Angeles Times)

It must have been good news to be cast in this series, but I’m sure it was also scary.

Harrison: Initially, I was terrified. I didn’t know whether it was appropriate for me to be cast. I was 27, 28 years old, had just started acting and hadn’t lived that much life. I feel I have gotten the benefit of Dr. King’s and Malcolm’s work, but what was it that I could do to bring a further understanding of it? Then I thought, “I just have to get over myself.” The producers told me Dr. King was young when he began his journey. There was a lot of responsibility bestowed on him. Plus, he had a wife and kid. I felt a little naive, but that also fits in with the story we’re telling. It’s about taking on that naivety and not mistaking it for ignorance or a lack of intelligence. It’s also about not losing that sense of hope that we have in our country and our identities in who we are, putting one foot in front of the other and walking in faith. Then I got excited thinking, “I can’t believe I get to go on this journey.”

Pierre: I share that sentiment. I’m the same age as Kelvin. When I got the call, I questioned whether I had the capacity, the endurance, the durability, the emotional intelligence, the life experience. I didn’t say yes immediately because I needed to sit with that and understand what that feeling was and how I was going to channel those feelings into something that would propel me forward as opposed to prohibiting me. Once I thought I could do that, largely because of the support network about me personally and creatively, I knew I could begin embarking on the journey. You find joy in it, which is so important because what these men did needs to be celebrated and championed.

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1. Aaron Pierre as Malcolm X in “Genius: MLK/X.” (Richard DuCree / National Geographic) 2. Kelvin Harrison Jr. as the Rev. Martin Luther King Jr. (Richard DuCree / National Geographic)

What was the research process like?

Pierre: We both watched and absorbed a tremendous amount of historical footage. I went to “The Autobiography of Malcolm X,” which is something I think I will revisit more than once in my lifetime. Then there’s “The Sword and the Shield: The Revolutionary Lives of Martin Luther King Jr. and Malcolm X,” which I trusted implicitly with its historical knowledge and insight. I visited Harlem, which fueled me in a very beautiful way.

Harrison: My initial instinct was to watch every movie about Dr. King, but my young actor brain and every actor I respected said, “Stay away from doing that.” So I refused that impulse. Then I had to figure out what those actors did. What I found out is that they brought a little bit of themselves to the role. I had to do an investigation of myself to figure out how to bring my humanity.

To prepare for their roles, Aaron Pierre, left, with Kelvin Harrison Jr., says they “both watched and absorbed a tremendous amount of historical footage.”

(Christina House / Los Angeles Times)

Aaron, were you intimidated by Denzel Washington’s acclaimed performance as Malcolm X in Spike Lee’s film?

Pierre: Denzel is a hero of mine. I have the utmost respect for him, not only artistically but personally. I had to manage that a hero of mine had played a hero of mine. I dealt with that by accepting that truth and then setting it free. Once I did that, I was able to permit myself to be liberated and safe enough to explore my own portrayal and bring my own life experience to Malcolm.

Kelvin, you had a similar situation. The actors who have played King include Jeffrey Wright and James Earl Jones.

Harrison: It’s kind of none of my business at a certain point. Dr. King was called to do something. If the people behind this project are calling me to do this, they see something in me I can’t see. And it’s arrogant for me to sit there and debate about it.

Pierre: At a certain point, we made peace with that fact, realizing all we can do is do our best. We use everything in our power to serve these tremendous men and their stories and legacies. Beyond that point, we have to set it free and let it be. It’s the only way to protect your well-being.

King and Malcolm X’s stories are told on parallel tracks. You share only a few scenes, but it’s clear you felt connected to each other.

Pierre: Absolutely. Aside from the professional work we share, this is one of my dearest friends. There’s a true sense of support and seeing one another through each others experience. We have so many parallels and similarities of our respective lives. We didn’t see each other a lot on set, but when we did, we checked in with each other. We understood that what we were embarking on was not easy. It required vulnerability.

Harrison: One of the times we did connect was when he came over to my little apartment in L.A. He brought doughnuts and I cooked. We talked about everything — how our journeys were going so far. Then we watched “Devil in a Blue Dress” with Denzel and Don Cheadle. We filled our cups with these beautiful portrayals. It was inspiration. It’s so easy to want to retreat when you’re on a journey like this. You get overwhelmed. You want to say, “This is too hard, I’m backing out.” So it’s important to have those moments to reconnect and say, “We’re in this together.”

The actors say they tried to support each other in their roles. “We talked about everything — how our journeys were going so far,” says Kelvin Harrison Jr.

(Christina House / Los Angeles Times)

What was the most challenging day for you both?

Pierre: If we’re being honest, every day was challenging. This isn’t an engagement that ended with the final scene of the day. This demanded that we be engaged every day for the five or six months we did this. Every day we felt the weight of wearing those jackets.

Were you ever able to relax? What did you do to relieve stress?

Pierre: I’m really very grateful to Kelvin and Weruche. I have a tendency, no matter what the project is, but particularly with a project of this magnitude, to completely immerse myself for the duration. But they really looked after me. I would just be sitting in my trailer, in the suit with the glasses on, waiting for the next scene. Then one or both of them would drop by and say, “I brought you some shrimp.” They would bring joy. They contributed to the health of my personal well-being.

Harrison: I read somewhere that Martin’s favorite show was “Star Trek,” and he would watch that to decompress. So I thought, “I’ve got to find my own show.” So I got addicted to “Big Brother.” That was my “Star Trek.” I know that show is ridiculous, but I refuse to give it that label because it’s so good. It was like, “They’re stuck in this house. On the set, I’m stuck in this universe.” I related to them, and it would make me laugh and have fun.

What do you think audiences will learn from “Genius”?

Pierre: I hope it will dispel the myths and reveal the truth about the experiences of these men. There is a considerable amount of misinformation about Malcolm X. They need to gain the understanding that he operated from a place of love and light. Some might say he was advocating for physical engagement. I disagree. I think he was advocating for safeguarding and preserving the safety and livelihoods of your loved ones, your community and for those who look like you.

Harrison: Our job as storytellers is to inspire. With this story, I see it as a mirror to our country and the cyclical nature of it.