SPOILERS ahead! It's been just a few days since Split emerged victorious with a dominant box office victory with just over $40 million, which represents eight times its $5 million budget. Many fans are still talking about the iconic twist that no one saw coming, which also paves the way for M. Night Shyamalan's next movie that fans have been waiting more than a decade for. Today, both M. Night Shyamalan and Split star James McAvoy discussed how that twist came to be, and how it will lead into either Split 2 or Unbreakable 2. If you haven't seen Split yet, there will be HUGE SPOILERS below, so read on at your own risk.

Fans were quite shocked to learn that the entire story told in Split, which takes place in M. Night Shyamalan's hometown of Philadelphia, was actually set in the same universe as Unbreakable, with the final scene revealing Bruce Willis' surprise cameo as David Dunn. The scene takes place in a diner, where a news report is playing about the Split character Kevin Wendell Crumb, who plays host to 24 distinct personalities, and has been given the nickname The Horde by the press. When one woman mentions another criminal that had a unique nickname, we see David Dunn telling her she's referencing Mr. Glass, Samuel L. Jackson's character from Unbreakable. M. Night Shyamalan revealed in an interview yesterday that his next movie will be a follow-up, featuring Kevin Wendell Crumb from Split, alongside David Dunn and Mr. Glass from Unbreakable. So will this new project be called Split 2, or Unbreakable 2? During a new interview with Empire, the filmmaker wouldn't reveal a title, but suggested that it could be something else different entirely.

RELATED: Petition Demands M. Night Shyamalan's Split Be Removed from Netflix
"However you want to look at it. Maybe it's a new format, this movie, this movie and a final movie. I'm writing the outline now. It's weird. It's long. It's the longest outline I've ever had. It has so many characters. I hope if Split is a success, I'll have the opportunity to finish the story. I want to finish it, so this is the third one."

While it may be "the third one," that makes it trickier to determine a title, especially with characters from two previously-unconnected movies coming together. Perhaps 2 Split 2 Unbreakable would be a viable option, to borrow from Universal's Fast & Furious franchise. Jokes aside, Empire also spoke with James McAvoy, who revealed that when he first read the script, there wasn't this pre-credits scene at the end of the film with Bruce Willis' David Dunn, but there was an allusion to Unbreakable. Here's what he had to say below.

"When I first read the script, it wasn't there. There was some weird little allusion to the fact that it might be linked to Unbreakable, but it was so subtle I kinda discounted it. Then on the last day of rehearsals I was like, 'mate, is this thing linked to that thing?' It was honestly the most subtle thing you could ever have written. None but the greatest fanboy alive would ever have noticed it. So it went from being a tiny music cue to a whole fullblown scene with a major movie star in it."

In an interview from yesterday, M. Night Shyamalan revealed that there were versions of the script where Mr. Glass and David Dunn were still "actively battling" throughout the city, in the background of this story. However, he ultimately cut them from the story because it became too much of a distraction. Now that this showdown between Bruce Willis' David Dunn and James McAvoy's Kevin Wendell Crumb is set, with Samuel L. Jackson's Mr. Glass also in the mix, James McAvoy was asked if he's looking forward to squaring off with Bruce Willis. Here's what he had to say, revealing his colorful nickname for the actor.

"When two baldies go to war. My money's on B-Dog. I hope he lets me call him that."

It remains to be seen if any of the discarded ideas from the Split script find their way into the Unbreakable 2 script, or when M. Night Shyamalan will start working on the actual script itself. It also remains to be seen if this project will be produced by Jason Blum's Blumhouse and distributed by Universal Pictures, like Split and 2015's The Visit. All we do know is that the characters from Split and Unbreakable will eventually clash in a City of Brotherly Love showdown that could send fans to the theaters in droves.