[SPOILER ALERT: Don't read any further if you have yet to see the movie.]

"X-Men: Apocalypse" owes a lot to "X-Men: First Class." Especially its ending.

After hijacking the world's nuclear arsenal and assembling his Four Horsemen, Alpha mutant Apocalypse (Oscar Issac) uses Magneto (Michael Fassbender) and a swirl of CG to literally build a new world from what's left of the humanity's old one. And after several punch-happy attempts to physically stop Apocalypse, Professor X must battle him in the psychic realm.

This type of showdown is one fans of the comics and the '90s animated series have been dying to see for years. In fact, as James McAvoy revealed exclusively in an interview with Moviefone, audiences almost saw a version of this fight in his first "X-Men movie.

"We had a mind battle written into 'First Class,' between [Charles] and Emma Frost, and it was fairly epic -- and cataclysmic," McAvoy said. He elaborated that the battle between the two mutants would have taken place within a "city of the mind kind of thing," as the two would be "tearing each other through walls and buildings and all that stuff."

So why didn't the battle make it into "First Class?" Blame Christopher Nolan.
"'Inception came out, while we were planning it, and [the studio] just cut it," McAvoy said. "And this amazing action sequence that I was so pleased about doing -- it was the only action sequence I had -- turned into us just staring hard at each other. So I was glad we got a little bit of mind battle in it, and that was something I fought for to get into this movie."

What the actors didn't have to fight for is to ensure that their characters didn't get lost in the shuffle, as new mutants were added to the X-Men's already very-deep bench. From Jean Grey to Nightcrawler, several fan-favorite characters joined the roster, in a movie that has to service at least three main characters and an epic baddie making his first long-awaited, live-action appearance.

"There's so much trust. I just get my script in the mail [and do what is there]," Jennifer Lawrence revealed. "Oscar -- he was really involved, though, in shaping his character. Because he was going to be in so much make-up, he was meeting with [co-writer and producer] Simon [Kinberg] a lot -- he was more creatively involved than any of us were."
McAvoy chimed in: "There's room to get involved [with the story] once we're there, on set. There's room to move things around and inject things. And really, we all trust Simon because Simon is the guy who comes up with the great stuff every time we do it, so we trust 'im."

So we know McAvoy's favorite scene, but was Lawrence's?

"I loved doing our scene where I come to see [Charles] in his office, I felt that there was a lot of growth to our characters where we recognize that we differ in ideals -- but have more patience with each other.'

J-Law's hardest scene? "Being strangled by Apocalypse. That was the hardest, because I was in a harness, being lifted by my genitalia." Ouch.

While a fourth film in this series has yet to be officially announced, McAvoy has at least one idea for a scene between Raven and Xavier that he would like to see.

"I'd quite like to, one day, get us back to where we were in 'First Class' and actually just be like: 'Hey, give us a cuddle.' I don't mean like lovers, I mean like brother and sister."

"You want more cuddles," Lawrence joked. "You are so precious."

"X-Men: Apocalypse" smashes into theaters Friday.