Imagine some of the world's most iconic movies if they didn't star the actors that made the main character roles famous. Could you imagine Tom Hanks not portraying the character of Forrest Gump or Harrison Ford not playing Han Solo? Could you picture the films Pretty Woman or Avengers without Julia Roberts or Scarlett Johansson? What if The Matrix or Titanic didn't star Keanu Reeves or Leonardo DiCaprio? Well, that's exactly what almost happened.

There are so many movies that almost got made starring someone else that could have made things totally different. Some of the world's most famous celebrities might have had wildly different careers. And, it's not just that these actors couldn't do the films or lost out to another actor. The most interesting part is that most of these actors simply decided, for one reason or another, to turn down the film. As a result, some of them walked away kicking themselves. In other cases, they took other roles that allowed them to go on and make those movies hits.

Below, we documented 15 different actors and films that almost happened but didn't. These actors turned down what could have been some of the most lucrative jobs in their careers, and the folks who did end up playing each part after the original choice declined made tons of cash.

Which movie roles would you not be able to envision someone else playing? There's a pretty good chance that a couple of those are on this list. Don't forget to share and make your comments should we have missed any.

Sean Connery - Lord Of The Rings

While Sean Connery said that he never understood the films or felt attached to the scripts, you'd think he'd have acted his way through because his decision not to star in a movie he didn't quite understand cost him approximately $450 million.

Connery was offered $6 million per picture plus 15% of the box office profits (when, after the magic of movie accounting, might not have worked out to all that much if it was a net profit deal). Regardless, that's a lot of money to leave on the table.

He still says he didn't get the book, the script, or the film after he saw it. Looking back, it's probably for the best that Connery didn't land the role. Could you imagine Gandalf with a Scottish accent?

John Travolta - Forrest Gump

It's hard to envision what Forrest Gump would have been like if a disco-dancing hitman played the main character role. But, as Forrest says, life is like a box of chocolates; you never know what you're going to get. Maybe Travolta, too, would have won an Oscar.

At least in the case of Travolta, he turned down the part to play a role in a movie that resurrected his career. When he passed on Gump, he went and made Pulp Fiction with Quentin Tarantino, and it completely rebooted his acting career, making him a coveted A-lister again. Up to that point, his employment had really fizzled out.

In 1995, it became an Oscars battle between Forrest Gump and Pulp Fiction. Forrest Gump won six awards compared to Pulp Fiction's one. Hanks has stayed one of Hollywood's more highly sought-after actors. Travolta is still around, but considered by many to be somewhat off his rocker.

Will Smith - The Matrix

Will Smith has turned down some pretty big roles throughout his acting career. One of the biggest was the role of Neo in the Matrix films. Keanu Reeves wound up taking the spot and making over $250 million for his part in the three-film franchise. Another actor Quentin Tarantino got a big fat no from was Will Smith, who was up for the title role in Django Unchained before Jamie Foxx.

Smith says now that he wouldn't have made for a good main character and that he would have overacted the part, trying to change too much of the work. He's probably right. It's hard to see anyone else in the role, and the reason why he said no was that he didn't sink his teeth into the movie when it was pitched to him. He said it was difficult to explain the concept, and it wasn't until he watched the film that he "got it."

Will's wife, Jada, did end up in the films. So, I guess he got pretty close to the movies in some capacity.

Leonardo DiCaprio - American Psycho

The movie American Psycho is a cult classic, and it can be argued that it put Christian Bale on the map in Hollywood. But, Bale almost didn't get the part. Lionsgate reportedly offered DiCaprio $20 million to play serial killer Patrick Bateman, and he expressed interest which surprised everyone. As a result, the studio went as far as sending out a press release saying that he would star. Unfortunately, that's not who director Mary Harron wanted.

Harron had done an exhaustive search to land on Bale. And when the studio announced Leo's involvement, Harron was furious and Bale was devastated. Harron believed that DiCaprio had too young a fan base to see the movie and that his boyish looks made him absolutely wrong for the part. DiCaprio went on to do fine, but Bale became a huge star because of the film.

Al Pacino - Star Wars, Apocalypse Now, And Pretty Woman

Al Pacino is one of the best actors of his generation. He became known for the larger-than-life characters that he played. But, he was also extremely selective in what he chose to do, turning down some of the biggest acting roles in history. Not only did he pass on the role of Han Solo in Star Wars, but he also turned down the role played by Martin Sheen in Apocalypse Now and the role played by Richard Gere in Pretty Woman.

When asked why he turned down a role like the one in Apocalypse Now, it wasn't anything to do with understanding the script or some sort of principle as an actor. He turned it down because he felt that while Francis Ford Coppola was going to be up in a helicopter telling him what to do, he was going to be down and mucking around in a swamp for five months. He simply wasn't excited about that sort of work environment.

Emily Blunt - Iron Man 2

Emily Blunt turned down the role of Black Widow in Iron Man 2 over what she says is a conflicting schedule. Many others have stated that the real reason was a lower paycheck. If that's the case, Blunt has to be looking back at it now and seeing how much money Johansson made and kicking herself.

Blunt told Screen Rant that she had no regrets about missing out on the role but that she was still open to playing a superheroine in the future. Blunt has been very cordial when asked about the seemingly stupid decision not to take the part, citing Johansson as the better fit and that Scarlett nailed the role. Blunt is a big fan of The Avengers films and is confident that another opportunity will come along. She says she's never regretful about not taking a role, but this may be one of those exceptions.

Harrison Ford - Jurassic Park

Harrison Ford is the highest grossing film actor of all time. Could you imagine what his total would be had he agreed to the role offered by Steven Spielberg in the Jurassic Park franchise? Spielberg revealed that he not only offered Ford the role of Alan Grant (eventually played by Sam Neil), but before Jurassic World went through a series of rewrites, Ford was set to star in the reboot.

Ford claimed that the role of the Grant character wasn't a good fit for him, but one has to wonder what made him feel that way. It's not like there was much to that character. A paleontologist who needs to act surprised to see dinosaurs reborn, then try to survive when they turn on their creators. There wasn't a whole lot of depth to that character, and Ford would have had new action figures, collectibles, and all sorts of other goodies paying him handsomely.

Tim Roth - Harry Potter

Tim Roth was the number one choice to play Severus Snape in Harry Potter. The role went instead to Alan Rickman who made that character memorable. Roth said he "wasn't ready to be on a lunch box." He added that while his kids really wanted him to take the role, he didn't want to fly back and forth between two movies, and he felt that it just wasn't his time. He admits that Rickman was the right choice for the part.

The Harry Potter films were some of the highest-grossing films in history, and Roth could have been a very big part of that history. Instead, he'll forever be known as a talented actor who has taken a lot of great roles, but never really one that was a blockbuster moneymaker.

Rooney Mara - Rogue One

While some have gone as far as to suggest that the role of Jyn Erso in Rouge One was Rooney Mara's if she wanted it, Mara herself contends that she was never really in the running for the part. She says she met with director Gareth Edward and she really liked him but then she didn't end up reading for it. She was working, and it just wasn't the right thing or right timing. She simply decided not to read for it because she was already working six days a week and figured it wasn't going to be possible.

The movie has grossed over $1 billion, and while Felicity Jones wasn't expected to be seen in any of the sequels (due to how the movie ended), she did work in a sequels clause and made a seven-figure salary for the film. How she'd appear in another film is still unknown, but she'll be paid handsomely for it.

Elizabeth Olson - Star Wars: The Force Awakens

Elizabeth Olsen, Jennifer Lawrence, and Shailene Woodley were considered for the role of Rey, which went to Daisy Ridley. This would have been a huge opportunity for Olsen, but because of a commitment to Marvel Studios, she refused the audition. She ended up playing the role of Scarlet Witch in the Avengers' franchise and didn't do too shabby because of it. The shoot dates for The Force Awakens clashed with Age of Ultron.

This is the same actress who almost decided that she didn't want to act altogether. After seeing what happened with her two sisters (Mary-Kate and Ashley Olsen), she felt that a different path was better suited than Hollywood. For someone who changed her mind later in life, having an opportunity at The Avengers and Star Wars movies is incredible.

Johnny Depp - Titanic

In a phone interview on Howard Stern's show, Johnny Depp would not say which films he has turned down (rumors are there are ton of them, including Ferris Bueller, Hulk, Legends of the Fall, the Matrix and others) but Howard Stern reportedly got him to admit that he "labored" through the Titanic script. Imagine that. Not only did Depp not take the part, he thought the blockbuster was one of the worst scripts he'd ever read.

You could make a whole series of articles about the roles that Depp turned down that could have made him an even bigger star than he already is. You could also make a case for some of the stinkers he did choose. Would it have changed his stance now as the most famous Hollywood actor who is reportedly broke? Hard to say.

Tom Selleck - Indiana Jones

Harrison Ford has turned down a lot of work, but one of his more iconic roles, Indiana Jones, he almost didn't land. After using Ford in Star Wars, George Lucas was initially against using him for another of his movies. Both Lucas and Spielberg thought Selleck (who went as far as to do a screen test) was perfect for the part and were ready to shoot with him as the lead. Unfortunately for Selleck, the actor had already filmed a pilot for a CBS detective show called Magnum P.I. and couldn't get out of the contract.

Selleck did well with Magnum P.I. but Indiana Jones grossed over $1.8 billion. Perhaps even more than Han Solo did, the character of Indiana Jones went on to make Harrison Ford into one of the most famous and highest-grossing actors of all time.

Nicolas Cage - The Wrestler

After Mickey Rourke's stunning work as Randy “The Ram” Robinson in The Wrestler, it is hard to imagine anyone else playing the role. However, the part of the once famous but now tortured wrestler was first offered to Nicolas Cage. Had he taken it, Cage might not have become an actor known for straight-to-DVD releases. Mickey Rourke went on to do a handful of box-office smash movies and, in a way, rebooted his dwindling career.

There were rumors that Cage was dropped from the movie but he later went on to say that he chose to back out because of the time it would have taken him to get into the kind of shape that made him appear like a wrestler who was on steroids. He talked to Rourke about the job and felt that Rourke was better suited for it.

Matt Damon - Avatar

Matt Damon considered starring in Avatar just for the opportunity to work with director James Cameron. Instead, he chose to do the movie Green Zone which was a flop by many measures.

Fortunately, Damon has made plenty of good movie choices and a boatload of money. Had he not, he might have been kicking himself, considering that Avatar grossed over $2 billion (over $3 billion if you adjust for inflation).

To his defense, The Bourne Ultimatum was also shooting around the time Avatar was, so there were a couple of things that made it difficult for him to commit to the role. He didn't just pass it up because he didn't see an opportunity. Apparently, he also turned down the role of Two Face in The Dark Knight Rises.

Michelle Pfeiffer - Pretty Woman, Basic Instinct, Silence Of The Lambs

Pretty Woman, Basic Instinct, and Silence of the Lambs would have looked like very different movies if Julia Roberts, Sharon Stone, and Jodie Foster had not starred in each respective film. But, none of these women was the first choice for these movies. Michelle Pfeiffer was offered the lead roles and turned them down. For that reason, she takes the cake for the actor/actress who made the worst decisions.

Pfeiffer knows it too. She regrets declining all but one of the films. Because she was not prepared to do the nudity required in Basic Instinct and was worried that her father might see the film, she turned it down right away. However, she admits to being completely wrong about the other films. Pfeiffer admits to being completely clueless about the potential commercial success of the films she's asked to do.