Cillian Murphy 'knew' he was the wrong choice to play Batman in Christopher Nolan's 'Dark Knight' trilogy, and says getting into Val Kilmer's Batsuit was an 'operation'

• "Oppenheimer" star Cillian Murphy auditioned to play Batman in Christopher Nolan's "Batman Begins."
• The Irish star said he "knew" he was wrong for the role.

2023's "Oppenheimer" marks the sixth project between director Christopher Nolan and Irish star Cillian Murphy in the last 20 years, after they first partnered up for "Batman Begins" back in 2005.

The 47-year-old actor played the psychotic villain, Scarecrow, opposite Christian Bale as Bruce Wayne in the groundbreaking reimagining of the Caped Crusader.

But Murphy originally auditioned to play the Dark Knight himself, and fans got a glimpse of what his version of Batman would've looked like in a documentary about Nolan's Batman trilogy.

Appearing on the "WTF with Marc Maron" podcast Monday, Murphy said that he "knew" he was wrong for the role.

"So, that was 20 years ago. I think he'd seen '28 Days Later,' actually. We met up here in LA. He, for some reason, wanted me to screen test for Batman, which I think I knew, and he knew, I was wrong for. And then he saw something in that and cast me as Scarecrow," said the actor.

Asked why he wasn't sure about the role, Murphy said: "I don't think I'm the physical specimen to play Bruce Wayne."

Murphy recalled trying on Val Kilmer's Batsuit for the screen test, explaining that it was difficult to get into, but everyone who was auditioning for the role wore it.

"I actually tried on the Val Kilmer suit in the test, it's quite roomy. It's a fucking operation getting into those things, though," Murphy said.

While he knew he wasn't the right person to play the billionaire vigilante, Murphy said he just enjoyed the chance to wear the Batsuit and audition for Nolan.

"It wasn't right. It wasn't right. Imagine this, I'm getting to try on a suit, a Batman suit, on the Warner's lot, and do a screen test for Christopher Nolan. That's all my expectations were at the time," said the "Peaky Blinders" star.

The actor also praised Bale for his work as Bruce Wayne in the "Dark Knight" trilogy, adding: "He transformed himself into that role, and he's done it many many times. I think he defined that role as Batman."

"Oppenheimer" is in theaters Friday.