Even with worldwide fame, Robert Downey Jr. can still have a fanboy moment — and says he did just that with Beatles legend Paul McCartney.

During an appearance on “Jimmy Kimmel Live,” the actor recounted how he invited a group of people to attend a screening of “Oppenheimer” in New York’s Hamptons, where he has a home.

He said he couldn’t attend a premiere for the film or promote it due to the actors strike, which kicked off ahead of the blockbuster film’s July release.

“I invited everyone who was in the Hamptons, and for the first time in my whole career, strangely, everyone RSVP’d,” he told Jimmy Kimmel.

Guests included iconic actor Michael J. Fox and director Stephen Spielberg.

“And then I sit down, and the movie starts and I realize I’m sitting next to Paul McCartney,” he said. “And I was like dude, Paul McCartney RSVP’d and he’s sitting next to me.”

“And then I was just like, smelling his cologne, and I started like, breathing in the same rhythm as him,” he added. “I didn’t even watch the movie.”

“I still find myself getting starstruck and fanboying out all the time,” he said.

Downey Jr. won a Golden Globe on Sunday for his performance in “Oppenheimer,” the epic thriller about the eponymous physicist known as the “father of the atomic bomb.”

Watch his interview on “Jimmy Kimmel Live” below.