The third in a trilogy so long in the making.. well, it's honestly a miracle it was finished. Kevin from Split was supposed to be introduced in Unbreakable, the story goes, but keeping the story concise meant cuts had to be made. By the time Split was produced, it was under a different company. Somehow M. Night convinced them to work together and allow the third movie of the trilogy to be made. That's an even bigger twist than he could come up with himself, I'd say.