Christopher Nolan’s latest film, "Oppenheimer," has become one-half of the box office and pop culture phenomenon "Barbenheimer," sweeping up glowing reviews along the way.Video above: 'Barbenheimer' fever sets box office recordsBut eagle-eyed fans have spotted a mistake in a scene set in 1945, as Cillian Murphy's J. Robert Oppenheimer stands among a crowd waving American flags – bearing the wrong number of stars."It was good and all, but I'll be that guy and complain they used 50-star flags in a scene set in 1945," Twitter user Andy Craig wrote on Friday. In 1945, the American flag featured 48 stars, as Alaska and Hawaii hadn't yet become U.S. states. It wasn't until July 4, 1960, that a 50-star flag was first flown in the U.S. But the correct American flag flies behind Oppenheimer in another scene set in the same year. One Twitter user had a theory: "I can argue that this is done intentionally as the colored scenes were from Oppenheimer's perspective, while the black and white scenes were from another. This would be a memory of Oppenheimer from his present-day memory which does have 50 states on the flag."The film depicts the events of Oppenheimer's life, flitting between his days as a student in the 1920s, his time overseeing the development of the nuclear bomb during World War II, and the U.S. Atomic Energy Commission committee hearings in 1954 during the McCarthy era, in which he was stripped of his security clearance due to his associations with the Communist Party. "Barbie called this in didn't she," another Twitter user joked, referencing the fact that "Oppenheimer's" release date coincided with Greta Gerwig's "Barbie."Coming in behind "Barbie," "Oppenheimer" opened at $80.5 million in the U.S. over the weekend, according to Comscore. Both movies essentially doubled predictions from weeks ago, Paul Dergarabedian, senior media analyst at Comscore, said.It's unprecedented to not only have two films do so well, but also to help each other with the "Barbenheimer" trend, Dergarabedian said.