In the final version we get to see in cinemas, the climax takes place on a train as the X-Men try and fend off dozens of shape-shifting aliens who are trying to get to Jean Grey. Later, Jean takes on and defeats the leader of the shape-shifters, sacrificing herself in the process. But in an interview with ReelBlend podcast (via SlashFilm), Tye Sheridan who plays Cyclops in Dark Phoenix reveals that the original ending of the film was actually much different. Not only would it have resulted in the X-Men getting dissolved in a similar fashion to the Avengers in Captain America: Civil War, the shape-shifting villains were initially supposed to be Skrulls.
And then Jean comes down in the front of the U.N., and causes… there is this huge battle between the guards at the U.N. and Jean Grey, and all the guards turn out to be Skrulls. And then Jean and Scott are — Scott is fighting Skrulls in the fountain. He gets thrown into the fountain in front of the U.N. And then Jean comes down and basically fights all of the Skrulls off, and then blasts back off into space. [She] basically says goodbye to Scott and Charles. And then it’s all over, I guess.” The Skrulls idea certainly makes sense. In the comics, the X-Men have faced off against the shape-shifting alien species known as the Skrulls multiple times. However, the Skrulls were also featured heavily in Captain Marvel earlier this year, so perhaps that’s why director Simon Kinberg found it necessary to change the name of the villainous species to D’Bari. The ending with the President of the United States and the U.N. is certainly more interesting. However, given the film’s short runtime and rushed nature, perhaps this original ending would’ve been another case of a great idea left unexplored.