'Oppenheimer' star Matt Damon said kissing Scarlett Johansson was 'hell' because of an onion sandwich

• Matt Damon and Emily Blunt got on the topic of bad breath during a recent interview promoting "Oppenheimer."
• Damon recalled the time he had to kiss Scarlett Johansson after she ate a meal full of onions.

Matt Damon took a walk down memory lane to reminisce with his co-star Emily Blunt about the "horrible" time he had kissing Scarlett Johansson.

Damon and Blunt, both starring in Christopher Nolan's "Oppenheimer," joked about whether they should let someone know if they have bad breath — both strongly agreed you should — when Damon brought up his time filming the 2011 movie "We Bought a Zoo."

"It was hell," Damon said in an interview published Wednesday with LADBible.

Damon explained to Blunt that he and Johansson had shot an intimate scene that ended in a kiss before eating, unaware that they would continue locking lips after lunch.

"We went to lunch and she and I both thought it was over and she ate like an onion sandwich," Damon said. "And she came in and Cameron Crowe had set the camera up and it was like a tight shot of the kiss. And she goes 'Aw shit! I literally just had – I had like an onion sandwich.'"

Blunt then asks Damon whether or not he was still "slightly aroused" while filming the scene.

Damon said although he made fun of her the entire time, her breath smelled like "roses."

Damon, who plays Leslie "Dick" Groves, a US Army officer who led the Manhattan Project, and Blunt, who plays Kitty Oppenheimer, the wife of J. Robert Oppenheimer, star alongside Cillian Murphy and Robert Downey Jr. in the story of of the development of nuclear weapons in the US.

Representatives for Johansson did not immediately respond to Insider's request for comment.