"Oo-ee-oo-ee-oo, wah-WAH-wah..."

Half a century later, Ennio Morricone's theme from "The Good, the Bad and the Ugly" remains one of the most instantly recognizable and unforgettable pieces of movie music ever. Even if you haven't seen Sergio Leone's epic Western, you know the tune, and you've probably heard it in other movies and TV shows as some gunslinger sauntered into a dust-blown vista, ready for a shootout. But none of those gunslingers was as badass as Clint Eastwood, who cemented his icon status for all time when this film opened 50 years ago this week, on January 18, 1967.

As familiar as the movie, its antihero, and its music have become over the decades, there's still plenty you may not know about the classic spaghetti Western, from how stars Eastwood and Eli Wallach were nearly killed many times on the set, to how the director injured himself in the crotch with a revolver, to Eastwood's biggest complaint about the film that made him an international star. Read on to learn the movie's secrets -- good, bad, and ugly.
1. "The Good, the Bad and the Ugly" is famously the third movie in Leone and Eastwood's "Dollars" trilogy, but it's actually a prequel to the other two. Notice how it's not until the final minutes of the movie that Eastwood's Man With No Name (here, nicknamed "Blondie") picks up the iconic poncho he wears in "A Fistful of Dollars" and "For a Few Dollars More."

2. Eastwood was reluctant to make a third picture with Leone until he negotiated a deal that gave him $250,000 up front plus 10 percent of the North American profits -- and a new Ferrari. Not too shabby.
3. Leone (above) was warned against making the picture by no less than Orson Welles, who claimed that movies set during the Civil War were box office poison.

4. Having studied Matthew Brady's famous Civil War photographs, Leone would insist that his movie, shot in Spain with a largely Italian cast, was more historically accurate than American-made Westerns. There were still some anachronisms, though, like the use of dynamite, which wasn't invented until two years after the war ended.
5. To play colorful Mexican bandit Tuco, Leone wanted to cast "Fistful" and "Few" co-star Gian Maria Volonte, but the director decided that Volonte wouldn't bring the necessary humor to the part. The director ultimately picked Wallach, who'd played similar parts in "The Magnificent Seven" and "How the West Was Won."

6. For the merciless Angel Eyes, Leone wanted Charles Bronson, but the actor was committed to making "The Dirty Dozen." He also considered "Dozen" co-star Lee Marvin and Henry Fonda before going with Lee Van Cleef, who'd played Col. Mortimer in "For a Few Dollars More."
7. Eastwood warned Wallach, who was new to spaghetti Westerns, that the Italian crew would be unreliable when it came to safety issues. Indeed, Eastwood himself was nearly decapitated by a chunk of flying debris during the bridge detonation scene; you can see it in the finished film flying inches from his head and landing a couple feet from the actor.

8. Wallach, too, was nearly decapitated during the scene where Tuco lets the train pass over him to sever his chains. Fortunately, Wallach kept his head down, since the crew hadn't accounted for the exterior steps jutting out from the train's cars.
9. Wallach also accidentally drank acid that a special effects crew member had poured into a lemon soda bottle, but he spat it out before it could do any damage. And during one scene, while Wallach was on horseback with his hands tied behind his back, the horse got spooked by a gunshot, galloped away, and ran a mile; miraculously, the actor didn't fall off and get trampled.

10. Nonetheless, Wallach practically stole the movie from Eastwood, who complained that Tuco came off as a more fully fleshed character than Blondie. That wasn't just because of the script giving him some backstory. Wallach claimed he'd improvised some of Tuco's best bits, including his playing with the guns in the gun shop (something the actor said he did because he was still a novice with guns), his shoving the "Open"/"Closed" sign in the shopkeeper's mouth, and his line, "When you have to shoot, shoot! Don't talk!" Wallach said he didn't mean for that line to be funny, but it made the crew laugh, so Leone kept it.
11. It might have helped Wallach that he was the only one of the three stars who could speak to the director without an interpreter. Even though Eastwood and Van Cleef had worked with Leone before, neither star could speak any Italian. Nor could Wallach, but he and the director communicated in French, which Wallach spoke poorly and Leone spoke fluently.

12. Leone had some odd ideas for Tuco's costume. Wallach said he chose to wear both suspenders and a belt because that's how Leone dressed. The director also wanted the actor to wear a gun dangling from a rope instead of a holster.

13. Demonstrating how Tuco might swing around to reach for the gun, Leone ended up hitting himself in the groin with the firearm. He ultimately decided Tuco could carry his pistol in his pocket.
14. The movie is well known for being spare with dialogue. There's none at all in the first 10 minutes of the movie. And the famous showdown among the three leads near the end -- a master class in editing -- ratchets up the intensity by cutting back and forth among the three gunmen staring each other down wordlessly for nearly three minutes.

15. Leone would shoot and edit the film to fit Morricone's music, rather than have the composer watch the completed film and then time the music to fit the shots. The reason, apparently, was that when Morricone would watch the footage, he'd inevitably annoy Leone by cracking up into helpless laughter.
16. The film cost $1.2 million to make. It earned back $25.1 million.

17. In 2002, Martin Scorsese helped restore 14 minutes cut from the American release. The footage was all in Italian, so Eastwood and Wallach had to re-dub their lines into English. Simon Prescott subbed for Van Cleef, who had died in 1989.
18.Stephen King has cited Eastwood's performance in this film as an inspiration for protagonist Roland Deschain in his "Dark Tower" saga.

19.Quentin Tarantino has called "The Good, the Bad and the Ugly" his "absolute favorite movie and the greatest achievement in the history of cinema." You can find homages to it throughout Tarantino's work, from the three-way showdown at the end of "Reservoir Dogs" to the hiring of Morricone to score Tarantino's 2015 Western "The Hateful Eight."