Chan, 39, posted a series of behind-the-scenes photos on Instagram Thursday that were taken while filming the Marvel movie, which hit theaters in November. Eternals is now on streaming, becoming available to watch on Disney+ this past Wednesday.
To mark the occasion, Chan shared memories of herself hanging with the cast and crew — including never-before-seen looks at Styles, 27, in costume as Eros/Starfox.
In the first photo of herself and Styles, Chan and the "Watermelon Sugar" singer pose in their armor, showing off his red and gold costume and her green and silver one.
While the costars serve a serious stare at first, they break out into smiles in a second photo that appears to have been taken in the same moment. Styles smiles and holds his hands out beside him, while Chan stands beside him and beams at the camera.
In the comment section, Olivia Wilde reacted to the photos of boyfriend Styles, writing, "Watching now obviously 🙌🙌🙌."
Steve Granitz/FilmMagic; Kevin Mazur/Getty Olivia Wilde and Harry Styles
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Chan stars in Eternals as Sersi, one of the 10 titular superheroes tasked with saving earth from the Deviants. While Chan's casting was announced long before Eternals premiered in theaters last fall, Styles' role was kept secret until the film debuted.
"I'm only in right at the very end," he said at the time. "But who didn't grow up wanting to be a superhero, you know? It was a great experience and I'm so grateful to have gotten to work with [director] Chloé [Zhao]."
Styles, who is set to appear in Wilde's upcoming film Don't Worry Darling plus the drama My Policeman, told Dazed he enjoys the "challenge" of acting.
"I like to challenge myself and do something different, and movies are definitely where I feel most out of my comfort zone," Styles said. "I'm coming from music where I don't think anyone really knows how it works, but I am somewhat in my comfort zone! But in movies, when I show up, I'm the new guy. I haven't been [an actor] for a long time and that's really cool, I feel like I've learned so much and life is about learning."
In an October interview with Empire, Eternals director Zhao said she knew Styles was the one to play Eros in her film from the very start. She explained, "That's the character I had in my mind. But I never said once to [President of Marvel Studios] Kevin [Feige], 'Here's the character. Let's find an actor.' For me, it was a package deal. It's got to be Harry. That's how I pitched it to Kevin."