Dark Phoenix, the upcoming X-Men movie that is set to end this version of the franchise, had to undergo massive reshoots at one point that entirely changed the third act of the movie. Originally, we had been given reasons that seemed a bit generic, like the filmmakers wanting to ground the movie a bit more and whatnot. However, stars James McAvoy and Michael Fassbender have revealed in a new interview that the ending actually changed because it closely resembled another mystery, recently released superhero movie.

With the movie finally set to arrive in theaters next month, the cast has started making the press rounds to promote it. During a recent interview, James McAvoy and Michael Fassbender were asked about the extensive reshoots. That's when things got interesting, as McAvoy gave anything but a typical answer. Here's what he had to say about it.

RELATED: Dark Phoenix Director Has a Perfect Way to Bring the X-Men Into the MCU
"The end [of Dark Phoenix] changed a hell of a lot. The finale HAD to change. There was a lot of overlap and parallels with another superhero movie that came out... a while ago."

Michael Fassbender also chimed in, joking that "They had spies on set and basically stole our ideas." A little background to help unpack why this might be so interesting. Dark Phoenix originally wrapped filming in late 2017. The original ending was set in space. Director Simon Kinberg then had to coordinate massive reshoots and the ending was totally reshot to set it on Earth instead, which is going to be the train sequence that has been featured in the trailers. That brings us to these new comments. The actors didn't dish on what movie specifically they're talking about, but we can narrow it down a bit.

Since production originally wrapped before the reshoots, Thor: Ragnarok, Justice League, Black Panther, Infinity War, Deadpool 2, Ant-Man and the Wasp, Venom, Aquaman, Captain Marvel, Shazam! and Avengers: Endgame have all hit theaters. If we limit this to movies with space sequences in the third act, we're left with Thor: Ragnarok, Captain Marvel and Avengers: Endgame. In any of those cases, it's a Marvel Cinematic Universe movie, which falls under the Disney umbrella. Since the Disney merger with Fox closed in March, so does Dark Phoenix, technically speaking. Though, the deal was more or less done months before that. Assuming the two companies were thorough, Disney would have realized Dark Phoenix resembled one of their movies some time ago. Hence, that could explain the reshoots.

As for which movie it could have been specifically? Best guess is Captain Marvel. Simon Kinberg previously stated in an interview they redesigned Jean Grey's Phoenix to be more "cosmic" and less "flamey." That sounds like they may have been pivoting away from looking too much like Brie Larson's titular hero. We may never know for sure, but this adds an interesting wrinkle to the whole situation. Dark Phoenix hits theaters on June 7. This news was first reported by Yahoo.