Cillian Murphy ‘smashed his head open’ on ‘Oppenheimer’

Call it Blunt force trauma or a real pillow case.

Emily Blunt revealed on Thursday night’s “Jimmy Kimmel Live!” that her “Oppenheimer” co-star, Cillian Murphy, smashed his head open while fluffing a pillow she gave him to help him sleep while shooting the boffo box-office movie.

Blunt, 41, was on ABC’s “JKL!” with Murphy, 47, and “Oppenheimer” co-star Robert Downey Jr., 58.

She told Kimmel how she bought Murphy, who stars as J. Robert Oppenheimer — the so-called “Father of the Atomic Bomb” — a special pillow to help him get a good night’s sleep.

But things went awry from there in the middle of the night.

“I just felt [what] Cillian needed, even more than food, was sleep on this movie,” Blunt said in reference to the “Peaky Blinders” star losing a lot of weight for the role to play the rail-thin Oppenheimer.

“So I got him this very beautiful pillow that I’m obsessed with … it’s a Hästens pillow. I gave him this pillow,” she said, asking Murphy if he minded her telling the story (he didn’t).

“He was really luxuriating in this pillow one night, and he woke up in the middle of the night — this is what he told me the next day — And he went to fluff himself back down in the pillow, misjudged where it was, and smashed his head open on the bedside table. 

“So he came to work, and they had to glue his head shut!” said Blunt, who plays Oppenheimer’s wife, Kitty, in the smash-hit movie, which garnered 13 Oscar nominations, including one for Murphy (Best Actor), one for director Christopher Nolan and Best Supporting Actress/Actor nods for Blunt and Downey Jr.

“I was a bit shocked you know!,” Murphy responded. “I was having a great sleep, and I had this amazing pillow, strange bed, strange table, [and] bang.”

Murphy then called the movie’s makeup artist, Luisa Abel, to help mend the wound so he wouldn’t miss any work.

“We were getting up at before it was bright, like at 2 a.m. or something, 3 a.m.,” he said. ” So I called her then, and I just came in, and then she glued my head, and covered it all up, and you don’t even see it in the movie, I think.”