Oppenheimer is getting a lot of buzz after a red, white and blue mishap.

During the period drama's opening weekend, some moviegoers spotted what appears to be mistake in a 1945-set scene where Cillian Murphy's J. Robert Oppenheimer stands in a crowd featuring several people waving American flags. The error in question? The number of stars on the flag during that particular year. 

"It was good and all," one user tweeted July 21, "but I'll be that guy and complain they used 50-star flags in a scene set in 1945."

After all, the American flag featured 48 stars in 1945 as Alaska and Hawaii didn't become states until 1959. And while two extra stars may not seem like a big deal for the movie prop, the user pointed out, "The pattern's different. Staggered rows vs. grid arrangement."

Adding to this flag conundrum is another 1945-set scene from the film featuring an American flag with the correct 48 of stars was being flown behind J. Robert Oppenheimer.

As such, another user actually thinks the 50-star flag in the scene wasn't an accident, after all the film spans 34 years, depicting the time J. Robert spent as a student in the 1920s all the way to the US Atomic Energy Commission committee hearings in 1954.

"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," the user posited. "This would be a memory of Oppenheimer from his present day memory which does have 50 states on the flag."

While many fans are buzzing over the possible prop error in Oppenheimer, the cast recently revealed the part of filming that awed them while on set: Cillian's intense diet to transform into the father of the atomic bomb.

"I love acting with my body, and Oppenheimer had a very distinct physicality and silhouette, which I wanted to get right," the Peaky Blinders star told the New York Times back in May. "I had to lose quite a bit of weight, and we worked with the costume and tailoring; he was very slim, almost emaciated, existed on martinis and cigarettes."

And his costar Emily Blunt echoed his sentiments, telling Extra earlier this month, "He had such a monumental undertaking, and he could only eat, like, an almond every day. He was so emaciated."

And you can see the transformation for yourself, as Oppenheimer is now in theaters. Now for more drastic movie transformations, keep scrolling...

Wahlberg shared a side-by-side photo of his previous toned physique alongside his look, which he achieved by gaining 20 pounds for his film, Stu. "From this 3 weeks ago, to this, now," he wrote, shouting out his chef, Lawrence Duran. "Thanks to @chef_lawrence_d cooking."

To play scientist J. Robert Oppenheimer in Christopher Nolan's Oppenheimer, the Irish actor "had to lose quite a bit of weight," he shared. "He was very slim, almost emaciated, existed on martinis and cigarettes." His diet? According to costar Emily Blunt, "He had such a monumental undertaking.And he could only eat, like, an almond every day."

For his Joker role, the Oscar winner opened up about his 52-pound weight loss, telling the Associated Press, "Once you reach the target weight, everything changes. Like so much of what's difficult is waking up every day and being obsessed over like 0.3 pounds. Right? And you really develop like a disorder."

The Parks & Recreation alum transformed into a fit superhero for Guardians of the Galaxy and never looked back.

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"I'd say my mother was worried," he previously told E! News after losing 30 pounds for Nightcrawler. "I would say she just wanted me to be careful. But she also knew and knows how seriously I take what I do and she respects that."

The actor bulked up for his roles in Whiplash and the Divergent franchise.

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The actress looked lean and strong for her starring role in The Girl With the Dragon Tattoo.

The Les Misérables star took home an Oscar for her role in the musical.

He's no stranger to morphing for movie roles. In 2004, he lost more than 60 pounds for his role in The Machinist, and he did it again for the film The Fighter, opposite Mark Wahlberg. He also gained 40 pounds for American Hustle—and lost 70 pounds for Ford v Ferrari.

The actor looked more like a god than a prince for his role in 2010's Prince of Persia. Gyllenhaal said he studied Parkour, the French art of street running, in order to bulk up for the film.

"All it is is time and discipline," the Oscar winner told Time magazine of his role in 2000's Cast Away, for which he lost over 50 pounds to play a man stranded on an uninhabited island.

The ripped rapper shocked fans with a photo of himself looking slender. He reportedly went from 214 to 160 pounds in just nine weeks to play a football player diagnosed with cancer in Things Fall Apart.

Shaping up for movie roles is nothing new. The legendary actor earned an Oscar nom for his role as terrifying tattooed rapist Max Cady in the 1991 thriller Cape Fear.

In order to portray former Vice President Dick Cheney in the 2018 biopic Vice, the star sported a fuller figure.