Jessica Chastain didn't know the name of her own character while she was filming Dark Phoenix. The 7th and final film in 20th Century Fox's mainline X-Men franchise was directed by Simon Kinberg and released in June, 2019. It received negative reviews from critics and relatively struggled financially, ending up as the second-lowest grossing X-Men movie overall behind the pandemic-released The New Mutants.
Dark Phoenix revisited the iconic X-Men saga of the same name with the franchise's second cast of characters, having previously touched on Jean Grey's transformation in the original trilogy's X-Men: The Last Stand. Sophie Turner of Game of Thrones fame reprised her role as Grey alongside other major returning characters, including James McAvoy's Professor X, Michael Fassbender's Magneto, and Jennifer Lawrence's Mystique. Chastain joined this group as Vuk, the leader of a shape-shifting alien race intent on destroying the Phoenix, and plays a crucial role in unleashing Grey's powers.
However, according to her recent interview on the Happy Sad Confused podcast, Chastain didn't know her character's name while filming Dark Phoenix. When asked about her and current Scenes from a Marriage co-star Oscar Isaac's X-Men experiences, the actress mentions that the project was caught up in the confusion of Disney's acquisition of 20th Century Fox, which might have caused crucial character details to get lost in the shuffle. She maintains that the director is blameless, though:
The reality is our situations were very different. My situation, I think the studio was bought at a certain point. I didn’t even know what my character’s name was until I saw the film… It was an interesting thing. But Simon Kinberg who directed it is an incredible human being and I’d work with him again. I love him.
Dark Phoenix's release was certainly complicated by 20th Century's sale to Disney, which took place from late 2017 to early 2019. The X-Men franchise had plans to continue its storyline with this cast of characters, but Disney CEO Bob Iger announced that any future projects would be under the umbrella of the Marvel Cinematic Universe, essentially ending Fox's franchise and de-incentivizing viewers from seeing its final installment. Dark Phoenix's post-production was severely impacted by the handover and understandably resulted in a chaotic final product.
However, Chastain's admission likely derives from the significant reshoots that took place for Dark Phoenix, which included major changes to her character. It was reported that the movie was changed to differentiate it from another superhero film, with early rumors and reports pointing to Dark Phoenix being too similar to Captain Marvel. Those reports indicated Chastain's character was originally meant to be a Skrull. So if her character's alien race was changed in post-production, it makes sense that she may not have known the new name until she saw the film. Still, Chastain's latest comment sheds light on just how much was changed in Dark Phoenix between the time of filming and when it released in theaters.
Source: Happy Sad Confused