Five years after Danny Boyle scared the hell out of audiences with 28 Days Later, his post-apocalyptic horror film, Juan Carlos Fresnadillo continued the story with 28 Weeks Later, which saw military forces attempting to secure a small "safe zone" for survivors in London while zombies raged all around them. To celebrate the sequel's tenth anniversary, here are 15 things you might not have known about 28 Weeks Later.

1. THE ORIGINAL STORY FOR THE SEQUEL WAS COMPLETELY DIFFERENT.

Titled 29 Days Later, the original sequel told the story of British marines attempting to rescue the Prime Minister and the Queen of England.

2. THE SEQUEL HAD A NEW DIRECTOR.

Instead of returning to the director’s seat to follow up his 2002 film 28 Days Later, Danny Boyle directed 2007’s Sunshine. He did, however, serve as one of the film's executive producers.

3. DANNY BOYLE DID MAKE A DIRECTING CAMEO.

In addition to his producing role, Boyle did step behind the camera—at least momentarily. He directed second unit footage of the opening scene.

4. BOYLE ALSO MADE HIS MARK ON THE PLOT.

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He suggested the eye hemorrhage to denote asymptomatic virus carriers.

5. THE NEW DIRECTOR GOT THE JOB BECAUSE OF HIS PREVIOUS MOVIE.

Boyle, sought out director Juan Carlos Fresnadillo to take his place because of Fresnadillo’s previous film, Intacto.

6. ROBERT CARLYLE HAD WORKED WITH DANNY BOYLE BEFORE.

Robert Carlyle was no stranger to working with Boyle; the two had previously worked together on Trainspotting and The Beach. Before accepting the role of Don in 28 Weeks Later, Carlyle had actually turned down the Major Henry West part in 28 Days Later (a role that eventually went to actor Christopher Eccleston).

7. THE HOUSE FROM THE OPENING SCENE MAY LOOK FAMILIAR.

It was the same home outside of London used in the film Children of Men.

8. THE DIRECTOR PUT IN A SMALL NOD TO HIS HOME COUNTRY.

Andy wears a Real Madrid jersey in 28 Weeks Later, which is a nod to Fresnadillo's home country of Spain.

9. ACTRESS CATHERINE MCCORMACK WAS BUSY DURING PRODUCTION.

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McCormack appeared in the play The 39 Steps in London at the same time she shot the movie, which required limiting her takes to simplify her schedule.

10. PRODUCTION DESIGNERS USED LITERARY AND HISTORICAL INSPIRATION FOR THE SCENES OF POST-APOCALYPTIC LONDON.

The empty and desolate street scenes were modeled after descriptions from Charles Dickens novels and from photos taken during the London Blitz from World War II.

11. THE FILMMAKERS CHEATED A BIT WITH THE POST-APOCALYPTIC SCENES.

Most of the end scenes were shot “day for night” to make it look like all the lights were out in London. If they actually shot at night they would have had to use costly CGI to remove the lights from shots.

12. BUT THE FILMMAKERS STILL HAD A LOT OF CGI TO COMPLETE IN A SHORT PERIOD OF TIME.

The production had to finish 400 CG shots in just two months.

13. THE PRODUCTION REALLY WENT UNDERGROUND.

By mattbuck, CC BY-SA 3.0, Wikimedia Commons

The film shot for two full weeks in London’s Charing Cross Underground station.

14. THE INFECTED CAST HAD A REAL CULTURAL PEDIGREE.

Everyone playing an infected person in the movie was required to have a movement-based artistic background. The final cast included ballet dancers, gymnasts, circus performers, and mimes.

15. THE FILM’S CODA WAS SHOT LAST.

The filmmakers came up with the idea for the coda just two weeks before production wrapped. Fresnadillo traveled to Paris with a limited crew and only HD cameras to shoot it in one afternoon.