Cillian Murphy calls 'Oppenheimer' costar Robert Downey Jr. the most 'unpredictably brilliant' actor he's worked with

• Cillian Murphy called Robert Downey Jr. the most "unpredictably brilliant actor" he's worked with.
• In a GQ interview before the SAG-AFTRA strike, Murphy praised his "Oppenheimer" co-star.

"Oppenheimer" star Cillian Murphy has nothing but praise for his costar Robert Downey Jr., calling him the most "unpredictably brilliant" actor he's worked with.

In a GQ Magazine interview from before the ongoing SAG-AFTA strike, Murphy spoke about his work with Downey Jr. in Christopher Nolan's new film.

"I mean, acting with him was just extraordinary," Murphy — who plays the titular theoretical physicist and so-called "father of the atomic bomb" J. Robert Oppenheimer — said. "He's just electrifying, the most available, engaged, present, unpredictably brilliant actor I've ever worked with."

Downey Jr. plays Lewis Strauss, chairman of the US Atomic Energy Commission and a major figure in nuclear weaponry after World War II who in the film rivals Oppenheimer and seeks to ruin his legacy.

Murphy also told GQ that while he had memorized the script for most of the movie, his scenes with Downey Jr. were "quite loose and quite improvisational."

Downey Jr. has also praised Murphy's hard work.

"Oppenheimer" was released in theaters last weekend and broke box office records as one part of the "Barbenheimer" cultural phenomenon with Greta Gerwig's "Barbie" movie.