Why Kate Winslet called out ‘Oppenheimer’ actor Robert Downey Jr.

This was one gig he couldn’t Sher-lock down.

Robert Downey Jr. revealed to Howard Stern that Kate Winslet couldn’t hold back her contempt over his attempt to pass for an Englishman during an audition for Nancy Meyers’ 2006 film “The Holiday.”

At a script reading with other actors hoping to land a part — including Winslet and Cameron Diaz, who were successful, and future “Tonight Show” host Jimmy Fallon, who, like Downey, didn’t book the gig — Downey and Fallon “both got called in just as seat-fillers,” the “Oppenheimer” and “Iron Man” actor recalled.

“Jack Black is getting his part and Jude Law is definitely getting my part, but [Meyers] needed someone to read with the gals, and we’re sitting there going, ‘It’s about to happen for us.’”

“I was like, ‘I’ve got to have a better English accent than Jude Law at this point,’ and Winslet said, ‘That is the worst British accent I’ve ever heard in my life,’” Downey confessed.

“I was like, ‘I’ll check out now, but I’m taking the gummy bears from the minibar.’”

Fallon, who was also present for the Stern interview, confessed to being so pumped to be in a hotel room reading the script that he would’ve done the movie at the time “for half-price” if Jack Black backed out.

The director let the pair down together, saying they weren’t “a perfect fit,” Downey added.

Fallon joked about never auditioning for another role because of the embarrassment.

“Without a doubt, I’m sitting across from Robert Downey Jr., and I go, ‘This is the best actor I’ve sat across [from] and did a scene with in my entire life,’” he recalled. “It was mind-blowing for me, and I quit the business. I never went back.”

The romantic comedy ended up starring Black and Law as the love interests to Winslet and Diaz, respectively.

Fallon joked that he got a tattoo of him and Downey — “us arm in arm, leaving dejected [after] not being cast in this movie.”

“That movie would have been so much better with the two of you guys,” Stern said.