'Moon Knight' star Oscar Isaac says his brother was his stand-in when he had to interact with himself

• In "Moon Knight" Oscar Isaac plays a character with dissociative identity disorder.
• The disorder means his character has multiple individual identities or personality states.

Oscar Isaac spoke about the challenges of portraying his character's dissociative identity disorder in "Moon Knight" during the show's press conference.

In the Disney+ series, which premiered on March 30, Isaac plays Steven Grant, a gift-shop employee who becomes aware that he shares his body with another person.

This is because the character has DID, which the Diagnostic and Statistical Manual of Mental Disorders describes as a psychiatric disorder in which a person shows at least two individual identities or personality states that can manifest through the person's behavior.

One way the series portrays this disorder is by having Steven communicate with his alter, named Marc Spector, through reflections.

During a press conference for "Moon Knight," Isaac explained that he got his brother Michael Benjamin Hernandez, who is an actor and journalist, to play opposite him during these reflection scenes.

"It's the closest thing to me there is on Earth," Isaac said. "He came in and he would play either Steven or Marc. Even did the accent and everything. So that was really helpful to have someone that's not only a great actor but also shares my DNA to play off of."

In the series, Steven has a quirky British accent despite the character originally being American. Isaac previously explained to RadioTimes that the accent was his idea.

During the press conference, the "Dune" actor went on to explain that he didn't anticipate the role to be as "technically demanding."

"[I] show up and decide which character I was gonna play first. And then try to block that out and give my brother notes and then do the scene and then switch characters and then figure it out," Isaac said.

He continued: "The most fun thing about acting is acting opposite somebody and letting something spontaneous happen that you didn't expect, but there wasn't really an opportunity to do that and still having to try to find what makes it feel spontaneous and not all planned out. So that was challenging."

Isaac's costar May Calamawy later praised the actor's performance, saying it was like interacting with "two separate people."

"I could feel the energy," the actress, who plays a new character called Layla, said. "I wouldn't even have to ask who he was. With Marc, I would find myself more guarded around. With Steven, I'd feel more nurturing. And there was no intellect or thought process involved in it. It was just visceral."

New episodes of "Moon Knight" are released on Wednesdays on Disney+.