So, Split is a secret Unbreakable sequel, Prometheus a not-so secret Alien prequel and 10 Cloverfield Lane a sort of side sequel to Cloverfield. We know all of that now, but at some point in the lifecycle of those movies very few if any were hip to those big secrets.
Welcome to the brave new world of experimental sequels/prequels. While the majority of Hollywood is busy planting release date flags for sequel after sequel a handful of producers have dared to wonder what a sequel/prequel would look like if they just pretended it was an almost if not entirely unrelated, original movie. The results have been mixed, yet also remarkably rewarding for the uninitiated who end up feeling stunned when the "this new thing actually connects to that other thing" moment happens. It's increasingly difficult to actually surprise audiences like that, but perhaps the financial success of all three movies will lead to Hollywood unleashing a couple more cloak-and-dagger franchise extenders in the near future. After all, both Prometheus and Split performed well enough to earn sequels, with Alien: Covenant due out in weeks and the recently announced Split/ Unbreakable sequel Glass due in 2019.
To wiki-recap:
Then in 2010 Lost's Damon Lindelof re-wrote the script, and the project was steered toward more of a spiritual prequel, with Scott telling MTV in early 2011, "While Alien was indeed the jumping-off point for this project, out of the creative process evolved a new, grand mythology and universe in which this original story takes place. The keen fan will recognize strands of Alien 's DNA, so to speak, but the ideas tackled in this film are unique, large and provocative."
The simple question remained whether or not Prometheus was an Alien prequel or not, but Scott, Lindelof and Fox's marketing department continued to resist offering a straight answer, lifting a page out of J.J. Abrams' mystery box playbook. They even created a viral campaign build around Michael Fassbender's android character David and a futuristic TED talk delivered by Guy Pierce's character Peter Weyland to steer the conversation away from "will there be a xenomorph in this movie or not?" and more toward "this movie looks fascinating all on its own."
However, all they ended up doing was frustrating and confusing audiences, and producing a film which, while admirable in its grand ambitions to explore the source of all life on Earth, feels at war with itself. Even when you watch it today you can still see Spaights' and Lindelof's rival scripts duking it out up there on the screen. It's no mistake then that the sequel is called Alien: Covenant, and the promised Prometheus 2 featuring Shaw and David traveling to the Space Jockey's home planet is now just a 2-minute prologue released online yesterday.
Whereas Prometheus was an Alien movie which took to pretending it was something different 10 Cloverfield Lane was a genuinely original concept which took to pretending it somehow had anything to do with Cloverfield.
And he further explained to Fandango: "This movie is very purposefully not called Cloverfield 2, because it's not Cloverfield 2, [...] So if you're approaching it as a literal sequel, you'll be surprised to see what this movie is. But while it's not what you might expect from a movie that has the name Cloverfield in it, I think you'll find that you'll understand the connection when you see the whole thing."
That connection turned out to be aliens and one added-in-post street sign clarifying the entire film takes place on 10 Cloverfield Lane. However, the film's sudden turn in its final act from claustrophobic hostage horror into War of the Worlds proved too jarring for some, yet completely expected by others since, hey, the movie does have Cloverfield in the title. Conspiracy theories ran wild about the studio forcing through significant re-shoots to tack on a Cloverfield-esque ending for marketing purposes. However, Trachtenberg steadfastly ignored such theories, and the film, jarring finale and all, was a surprisingly early financial success at the 2016 box office.
He took part in EW's big oral history about Unbreakable, testing the waters for fan and stakeholder interest in doing something more in that world. Meanwhile, he put his head down and plugged away at turning himself into a low-budget director working for Jason Blum. When he restored his bankability as a director (via The Visit) he went straight into Split, and successfully prevented anyone from guessing/spoiling his big secret, even removing the Unbreakabl twist from the test and press screenings. Twists are kind of his thing, to the point of annoyance, but "this whole movie is actually a sequel!" is a different kind of gotcha than "he's been dead the entire time!"
Yet he pulled it off. He fashioned Split into a quality standalone thriller which just happens to have a Bruce Willis cameo in a mid-credits scene. There was no dicking around with audience expectations ala Prometheus nor was there a "this is connected to that other thing, but you'll have to watch to find out how" tease ala 10 Cloverfield. It's the type of risk which would drive a marketing department mad, but it's one you can make when your film costs less than $10m to make. The lesson to all others who might try this is to formulate your plan right away. If your movie is going to be a secret sequel/prequel decide that right away and stick to it.
Now, if only Life had turned out to be a Venom prequel. Sigh.