It's no secret that making a film is tough work, and the director has a myriad of decisions he or she must make when putting together a project. Overseeing every last aspect from the script to production design, it's vital that they be on point for everything, because history has shown that even one bad call can make (or break) a movie. That's just the nature of the business.

One of the most important tasks when making a film is casting. Actors and actresses are frequently how casual viewers are going to remember a movie, so it's necessary to find the right thespians for the job during pre-production. Like most things on a Hollywood production, the casting process will go through an extensive brainstorming session as several possibilities are considered for the main roles. It's a good thing that happens, because some of pop culture's greatest works may not have captured the zeitgeist if certain options were chosen. Here are Screen Rant's 10 Terrible Movie Castings That Could Have Happened.

NOTE: We are not commenting on the acting ability of any of the actors listed here, just their fit for the parts being described.

The Lord of the Rings

Movie Castings Lord Rings Gandalf Connery

One of the many highlights of Peter Jackson's Oscar-winning Lord of the Rings trilogy was Ian McKellen's performance as Gandalf. Essentially playing two versions of the character, the actor perfectly encapsulated the fun-loving nature of Gandalf the Grey in The Fellowship of the Ring, before shifting towards a more authoritative and wise persona for the final two installments as Gandalf the White. Regardless of which wizard he was playing, McKellen became synonymous with Gandalf, and was even nominated for a Best Supporting Actor Oscar for his turn in Fellowship. It may be hard to believe, but he wasn't Jackson's first pick for the part.

The director first approached Sean Connery when he was developing the ambitious project. Though Connery is a fine talent with an Oscar of his own to his name, it's hard to see his suave gentleman schtick gel with the kind of performance that was needed to bring Gandalf to life. Picturing him saying some of McKellen's lines create images of a walking meme machine instead of the memorable leader we were lucky to see fight. Not only that, Connery turned the part down because he allegedly did not understand the script, so this one is a dodged bullet for sure.

Donnie Darko

Donnie Darko image with Vince Vaughn in movie theatre.

A young Jake Gyllenhaal too his career to the next level when he turned many heads with his impressive performance as the title character in Donnie Darko. He quickly became a cult figure for disenfranchised teens, as his moody and low-key portrayal captured the mindset of troubled youth, giving an entire segment of moviegoers someone to latch on to. He was so good in the part, that it's hard to picture anyone else in the movie, but the filmmakers originally did.

Coming off the success of Swingers, the Donnie Darko part was first offered to Vince Vaughn. And while the actor has proven he can be serious when the material's strong enough, even he knew he wasn't a good fit. In the film, Donnie is a 16-year old. When Vaughn was first approached, he was already 30. It would have been hard for audiences (especially teenagers) to buy Vaughn playing someone nearly half his age, especially since he didn't exactly have the boyish look to pull it off. In all likelihood, it would have derailed the film.

Star Wars

Movie Castings Star Wars Christopher Walken

Perhaps the most beloved character in the Star Wars saga (see: the closing scene of the second Force Awakens trailer), Han Solo is a permanent fixture of pop culture. He's defined by his roguish charm and no-nonsense attitude, which are traits that fit Harrison Ford like a glove. The actor was able to seamlessly fall into character and become the person, which is why so many fans are nervous about the prospect of recasting the role for the upcoming young Han Solo Anthology film. However, when casting Star Wars, George Lucas was reluctant to use Ford (with whom he worked with before) and tested several actors.

One of them was none other than Christopher Walken. Now, it's hard to find a cinephile that doesn't love Walken, who has delivered many great performances over the years in a diverse range of titles. But he may not have been the best fit for Captain Solo. Walken is commonly associated with playing odd people who are "out there," which in a way contrasts the confident bravado of Ford. That's not to say Walken as the Corellian smuggler wouldn't have been interesting; it's just that the character would have been transformed into something else entirely and altered one of Star Wars' strongest merits.

American Psycho

Movie Castings American Psycho Leonardo DiCaprio

In one of his breakout roles as a grown-up movie star (following his child appearances in works like Empire of the Sun) Christian Bale demonstrated his incredible method acting style and chameleon ability to immerse himself in his roles when he played Patrick Bateman in American Psycho. He was equal parts mesmerizing and chilling, and became one of the most fascinating characters to watch on-screen. As terrifying as it may sound, it really seemed like a part he was born to play and helped set up the unpredictable nature of Bale's career. But Lionsgate wanted to go in a different direction.

The studio was keen on the idea of having Leonardo DiCaprio play Bateman. Since the heartthrob was fresh off the record-breaking success of Titanic, it's easy to see why he was the top choice (it was an effort to boost the commercial nature of the project). However, DiCaprio backed out so he could make The Beach instead, and opened the door for Bale to step in. As acclaimed as DiCaprio is today (the Internet will not rest until he wins an Oscar), it's probably for the best this didn't pan out. At the time American Psycho was made, DiCaprio still looked incredibly young and he would have had a tough time passing for a sophisticated New York yuppie.

The Terminator

Terminator Movie Timeline Explained

There's really no denying that Arnold Schwarzenegger was made to play The Terminator. Nailing the essence and physique of a killer cyborg, he was an intimidating and frightening presence as he hunted for Sarah Connor and took on a police station singlehandedly. Even his now-iconic voice sounded robotic, with lines such as "I'll be back" being delivered as if they were fed straight from a computer program. But the man who would become James Cameron's good friend and frequent collaborator was not the director's first pick for the famous villain role.

Originally, Cameron wanted to go with football star O.J. Simpson as the T-800. He was vetoed by producers, who felt that the charismatic Simpson would not be able to convincingly play a killer. Fate had a truly twisted and ironic way of proving them wrong, but Arnold was clearly still the right choice. At the time, the unknown bodybuilder was easier to buy as the titular character than a famous face like Simpson, and The Terminator's success helped launch one of the finest action careers in the industry. Plus, the sci-fi classic remains a timeless film, still holding up more than 30 years after its release. With Simpson there, real life may have tarnished the final product.

The Shining

Best Unscripted Movie Scenes Shining Heres Johnny

When you think of Jack Nicholson roles, one of the first that comes to mind is Jack Torrance, the man who descended into insanity while watching over the Overlook Hotel in Stanley Kubrick's The Shining. The actor fit the part like a glove, as his crazed and unhinged acting persona proved perfect qualities for the film's build-up and ultimate climax. Responsible for one iconic moment after another ("Here's Johnny!") Nicholson put his stamp on the character and the film itself, creating something that was hauntingly unforgettable.

However, Kubrick initially considered Robin Williams for Torrance. What changed his mind is one of the more amusing anecdotes in Hollywood. After seeing Williams' performance in the comedy Mork and Mindy, Kubrick decided that the funny man was "too psychotic" for Torrance and went with Nicholson instead. Now, Nicholson is hardly known for playing characters who are mentally stable, so the reasoning for the switch doesn't make the greatest deal of sense. But one has to admit Nicholson owned the role, and it would have been a little jarring to see Williams (at the height of his comedic powers) play so against type and chase his wife with an ax. Nicholson made it easier to buy into the premise.

Dirty Harry

Movie Castings Dirty Harry Frank Sinatra

Inspiring just about every other action hero that would follow and cementing Clint Eastwood's status as a bona fide industry icon (after he played the Man With No Name), Harry Callahan of Dirty Harry was the ideal part for the actor to play. Personified by a trademark scowl and growl, the cop was a ruthless and intimidating screen presence, making bad guys genuinely fear for their lives. Callahan took no prisoners and proved time and time again he was in charge, becoming one of the genre's most fascinating protagonists in the process.

But when Warner Bros. was first developing the film, they viewed it as a vehicle for legendary crooner Frank Sinatra. However, the singer was unable to sign on, because a broken wrist he suffered while making The Manchurian Candidate made it impossible for him to wield Harry's gun. Sinatra is a star in his own right and put together an impressive filmography in his lifetime, it's just that when you think of him, a no-nonsense cop doesn't exactly spring to mind. Picturing the charismatic and charming Chairman of the Board beating down thugs just doesn't seem right when compared to the stern and stoic Eastwood.

The Matrix

Best Action Movies The Matrix

Keanu Reeves is an actor who probably won't win an Oscar by the time he retires, but the man is absolute gold when he steps into an action role. From Johnny Utah to John Wick, he's delivered in these types of films time and time again, with perhaps his defining performance coming in The Matrix. In the hands of just about any other actor, the blank slate protagonist Neo could have been a disaster, but Reeves was able to make his emotionally distant and aloof persona work perfectly with the nature of the character. It almost seemed like the part was written for him.

However, before choosing Reeves, the Wachowskis offered the role to Will Smith, but the Fresh Prince turned them down because he didn't exactly buy into their pitch for the film. When Smith eventually saw the film, even he admitted he would have screwed it up, so it's for the best the actor went in another direction. Smith is essentially a big man on campus type in Hollywood and has a larger than life personality that makes him stand out from the crowd. Neo was supposed to be an everyman before evolving into The One, so Reeves' everyman persona ended up being a better fit for the movie's purposes.

Bad Boys

Martin Lawrence and Will Smith in 'Bad Boys 2'

Giving Michael Bay his start as a feature film director and eventually becoming one of the standout entries of the action genre, Bad Boys is one of the most famous pieces of 1990s action cinema. Carried by the terrific chemistry between stars Martin Lawrence and Will Smith (and a killer soundtrack), the film subverted action movie tropes and started a franchise many can't wait to see return. But if it weren't for producer Don Simpson's bad behavior, audiences would have been treated to a very, very different pair of bad boys.

Long before Lawrence and Smith came on board, Bad Boys was conceived as a film titled Bulletproof Hearts and was intended to be a vehicle for Saturday Night Live stars Jon Lovitz and Dana Carvey. The duo attended a Las Vegas party with Simpson to celebrate their upcoming collaboration, and Simpson apparently partied too hard for Carvey's liking. After becoming repulsed by the producer's actions, Carvey dropped out and Bad Boys was forced to go in a different direction. Many action fans are probably thankful Carvey was so sensitive, since the original concept sounds more like an SNL skit than a true action comedy.

Rocky

Rocky Movie Stallone

One of the many reasons why the original Rocky is considered to be one of the greatest sports movies ever made is because writer/star Sylvester Stallone's own life mirrored that of the hero so closely. Like Rocky Balboa, Stallone was down-on-his luck in Hollywood and trying to make his big break. It was easy for audiences to seem themselves in the character, since he represented the blue collar, all-American nature of the everyman fighting for something better. Because Stallone was an unknown, Rocky became inspiring to many moviegoers, showing anybody could do amazing things.

When United Artists first began developing the project, they gave the producers a $2.2 million budget with the intention of casting a big name like Robert Redford or Burt Reynolds as the lead. When the studio was informed Stallone would not sell the rights to the screenplay unless he could play Rocky, United Artists reluctantly agreed and cut the budget in half. It may have made the production a little more difficult, but the decision ended up paying off in spades. You wouldn't believe an established A-lister like Redford as someone struggling to get by, or accept that they would lose the title fight. That would have been completely against what the character (and the film) was all about.

Conclusion

Hollywood is an interesting place of "what-ifs" and there are probably alternate universes out there where some of these castings actually happened, drastically changing how people view certain movies. Whenever we hear about an actor passing on a role or dropping out of a film, we're always left to wonder about the possibilities - even if their replacement ends up spinning the part into cinematic gold.

As always, our list is not meant to be all-inclusive, so be sure to share some of your favorite picks in the comments below. And be sure to subscribe to our YouTube channel for more fun videos like this!