World War Z was one of the biggest box office surprises of 2013. The big-budget zombie film, which faced several production delays and a rewrite of the entire third act, seemed destined to bomb. Instead, it ended up becoming Brad Pitt's highest-grossing film ever, earning a healthy $533 million worldwide.

The unexpected success of the film led to immediate talk of multiple sequels. In a recent interview at the Toronto International Film Festival, Pitt confirmed that Paramount is working on a script for the first follow-up now.

Speaking with Variety, Pitt said:

“We gotta get the script right first to determine if we go further.”

And that's no small task. As Pitt went on to explain, the time spent working on the first film has given them plenty of options for the second film:

“We have so many ideas on the table from the time we spent developing this thing and figuring out how the zombie worlds work... We think we have a lot of stuff to mine from.”

World War Z deviated significantly from the original novel by Max Brooks, mainly because the book's epistolary form made a straight adaptation impossible. That being said, if Pitt and his collaborators wish to truly expand on the zombie world they created, returning to the book would be a great start. Each chapter offers a unique character and situation that could potentially warrant its own full-length movie.

In reality, however, the sequel will need to feature Brad Pitt's character returning, which presents some interesting options.

[WARNING: WORLD WAR Z SPOILERS AHEAD!]

At the end of World War Z, Pitt's character figures out that zombies don't attack sick people, leading to the development of a vaccine that's actually a deadly, but treatable pathogen. By disguising themselves with the pathogen, soldiers are allowed to roam freely among the zombies and efficiently execute them.

On its own, this provides a pretty tidy ending, but there are many different directions that you could take in the sequel.

World War Z helicopter swarm
'World War Z'

What happens to all the zombies? Is the goal to kill each of them? In the zombie genre, there's always somebody out there who keeps working on a cure. Could a misguided scientist make the vaccine ineffective through an experiment gone wrong?

Or how about this one: in the aftermath of the zombie takeover, global politics are out of whack, leading a rogue dictator to amass a private army of zombies to...do something. Okay, okay, that's enough. I'll let the pros do their job.

What do you think of the unexpected success of World War Z and where would you like to see a sequel go in terms of plot? Let us know in the comments.

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World War Z is currently back  in theaters as a double feature with Star Trek Into Darkness.

Source: Variety