On teasing the audience with mutant deaths in the opening X-Men: Days of Future Past sequence and later in the film, Simon Kinberg says there was definitely a line. "The thing that's tricky about that is, you don't want the audience to think, 'Every time someone dies it's a trick, so I don't want to emotionally invest in them anymore.' But we wanted to establish Kitty's power as we've defined it, both visually and dramatically, as opposed to just verbally. And there's something radical about starting a movie with a bunch of characters and seeing how badass the villains, the Sentinels, are." On Wolverine surviving drowning, Kinberg says, "That was part of the challenge. Bryan and I asked, 'How do you actually put Wolverine in real jeopardy?' Not just getting shot or blown up. Bryan had some science for how the lungs would rebuild themselves."
About the scene where Quicksilver, played by Evan Peters, tells Magneto his mother knew a guy with his metal-controlling power, Simon Kinberg, laughing, says it was a little tease. "You know the intention of that tease. Hardcore fans will know. Some people who get that Magneto is a bit of a playboy will know." And finally, in the final shot in X-Men: Days of Future Past before the credits roll it is revealed that Stryker is actually Mystique. "We really wanted to do something subtle with Stryker in this movie," he said. "We wanted it to be the beginning of the origin of him. He's in the shadows most of this film. In some ways, Stryker was included in order to trigger something for Wolverine. How would it impact Wolverine, going back in time and seeing this guy who is going to manipulate him in the future. That was just interesting. Stryker's been interesting in the books and the Brian Cox version was fantastic. But the last moment in the movie with the Mystique reveal… there's for sure more to that. As we follow the characters in to X-Men: Apocalypse, we have to address that and make it a real thing."