Terry Gilliam's mind-scrambling sci-fi thriller 12 Monkeys celebrates its 25th anniversary this coming December. Starring Bruce Willis and Brad Pitt, the story imagines a disease-ridden future dystopia in which a convicted criminal is sent back in time to find answers regarding the man-made plague that has annihilated much of Earth's population.

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12 Monkeys premiered theatrically on December 27, 1995, costing roughly $29 million to produce before going on to gross more than $168 million worldwide. The film also earned star Brad Pitt his first Oscar nomination and Golden Globe win, cementing it as one of the best sci-fi movies not just of the '90s but of modern cinema. Ahead of its 25th birthday, here are ten behind-the-scenes facts about the making of 12 Monkeys fans need to know.

Terry Gilliam Had Final Cut

Given the rocky relationship he had with Universal while making Brazil in 1985, director Terry Gilliam only agreed to make 12 Monkeys if he retained control over the final cut.

Much to his surprise, the studio agreed under two conditions. One, the budget had to remain relatively small. Secondly, Bruce Willis (a big star at the time) had to be cast in the lead role of James Cole in order to ensure opening-weekend success at the box-office. Gilliam agreed and was given final say over the finished film.

It's A Remake Of A Short French Movie

Despite Terry Gilliam's claims of never seeing it before making the film, 12 Monkeys is directly adapted from the 1962 award-winning short French film La Jatee, directed by Chris Marker.

Told exclusively through still images, La Jetée follows a troubled man who is forced to traverse time and space in order to find answers to global devastation in the wake of World War III. Several recurring themes and concepts are shared in both films, which Gilliam credits Marker within the opening credits.

Bruce Willis Wasn't The Director's First Choice

Brad Pitt next to the monkey logo in 12 Monkeys

Terry Gilliam's first choice to play the role of James Cole was Jeff Bridges (Brazil star Robert De Niro was also considered), whom he worked with on The Fisher King a few years earlier. Universal wanted a bigger movie star to play the part, so Willis was cast instead. Ironically, Willis also auditioned for the role Bridges played in The Fisher King.

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Once he was cast, Gilliam gave Willis a list of "Bruce Willis Acting Clichés" to avoid. Willis took this advice to heart, as seen in his tortured performance that garnered serious critical acclaim. Moreover, Willis took a drastic pay cut just to work with Terry Gilliam, and he was only paid well after the movie was released. Needless to say, Willis' casting proved beneficial to 12 Monkeys.

The Hamster Factor

Gilliam fostered such a reputation for being a perfectionist on the set of 12 Monkeys that, after one specific instance, his crew dubbed his perfectionism The Hamster Factor.

During the scene in which James Cole (Willis) draws blood from himself, the shadow of a hamster running on its wheel is seen in the foreground. This innocuous detail would normally require little time to film, but Gilliam spent the entire day to get the scene just right. As such, the nickname was given, which was included in the 1996 making-of documentary, The Hamster Factor and Other Tales of 12 Monkeys.

Brad Pitt Was Deprived Of Cigarettes To Get In Character

For the iconic scene in which Brad Pitt manically spouts nervous, rapid-fire dialogue in the asylum, Terry Gilliam was deeply concerned that the then-novice actor would not be able to credibly pull off the speech. As a result, Gilliam resorted to sensory deprivation to elicit Pitt's award-nominated performance.

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Gilliam sent Pitt to work with a speech coach to prepare for the speech in question. But in the end, Gilliam simply took away Pitt's cigarettes as a means of getting him in the proper headspace to deliver the speech as written.

The TV Ball Was Impossible To Work With

One of the most lasting images featured in 12 Monkeys is the large, spherical "TV Ball" that simulcasts various video imagery of the futuristic dystopia. Believe it or not, the prop almost didn't make it into the movie.

The Ball Prop was so difficult to work with on the set that it became infamous among crewmembers. The electronics constantly failed to work, as did the hydraulics that allowed the prop to move up and down. The entire apparatus broke nearly every time it was used during a take.

The Logo Was Inspired By An Old Puzzle

The recurring logo designs and that of the title sequence of 12 Monkeys, which feature thirteen monkeys atop a revolving globe, are directly lifted from a 19th-century puzzle.

Created by Sam Lloyd in 1898, the "Get Off the Earth" puzzle features thirteen characters atop two round dials. When the dials are turned, one of the characters disappears from the frame entirely. The titular puzzle-piece used in the film reinforces the underlying plot and theme of the story.

Terry Gilliam Had A Near-Fatal Accident

In the middle of production on 12 Monkeys, Terry Gilliam suffered a near-fatal accident after being thrown off a horse. He returned to the set covered with fresh wounds and bruises.

When he returned to work to finish filming, Gilliam was less concerned about his physical injuries and more worried about how the accident would affect his creative vision. Despite having zero sound stages at their disposal, Gilliam ultimately delivered the film on time and under budget.

There Are Subtle M. Night Shymalan Connections

Although nobody could have known at the time, 12 Monkeys features an eerie amount of connections to the work of M. Night Shymalan. For instance, both 12 Monkeys and Shymalan's The Sixth Sense and Unbreakable take place in Philadelphia, Pennsylvania, and both star Bruce Willis.

Furthermore, at one point James Cole mentions in that "all I see are dead people," which is very similar to the most famous line of Shymalan's Sixth Sense, also starring Bruce Willis. Also, Franklin Field in Philadelphia is featured in both this film and Unbreakable.

The Movie's Ending Was A Sarcastic Suggestion

James and Kathryn go through the airport in disguise in 12 Monkeys

Gilliam originally wanted to bookend the film with close-up images of young James Cole's eyes. He continually bickered with producer Charles Roven, who preferred the scripted ending in the airport parking lot.

Stuck at loggerheads, Gilliam suggested an expensive and extremely elaborate compromise which called for two cranes, a huge collection of cars, and an entire parking lot to achieve. Hoping Roven would reject the idea and let him film the ending he intended (a close-up of the boy's eyes), Roven instead loved the idea and approved it. Gilliam shot the sequence and loved it so much that he agreed to use it in the final cut.

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