“If done properly, a twist ending can be very effective. It provides the audience with a jolt at the end that gives them a reason to actually think about the story. The problem with the twist ending, however, is that it involves purposefully withholding key information from the audience in the hopes that the “twist” will make it worth it. This creates several potential issues . . .”
That quote comes from Poewar and brings up the most important thing to recognize about Twist endings, they’re dangerous. Remember the narrative structure we have been developing up until now. Your stories are supposed to be a coherent series of actions that ask questions and have a definitive ending. The Twist, if done poorly, throws this completely out the window. You are asking your audience to believe that everything you’ve told them up to that point is a lie, and that if they were more clever they would have seen it. To hide the twist from prying eyes, usually the clues are so thinly characterized as to be impossible to see except for in hindsight.
In short, because it’s nearly impossible to discover the twist until after the fact, your story becomes completely defined by the twist. Which is OK in some cases but it’s something you need to understand completely going into it.
That reminds me, I am talking about twists and I haven’t mentioned M Night Shyamalan yet. We can’t have that. Let me leave you this quote from his Wikipedia article,
Some critics have suggested that he would be more successful by hiring a screenwriter to help translate his stories to the big screen. He has also been labeled a “one-trick pony” for his continuous use of what some people call the “twist” element in his screenplays. After the release of The Village, Slate’s Michael Agger noted that Shyamalan was following “an uncomfortable pattern” of “making fragile, sealed-off movies that fell apart when exposed to outside logic.”
In a May 31, 2008, interview with the London Independent, Shyamalan offered this answer to the question about his “one-trick” movies: “Q: A common misperception of me is … A:That all my movies have twist endings, or that they’re all scary. All my movies are spiritual and all have an emotional perspective.