When production for Lord of the Rings began, Stuart Townsend, a relatively unknown actor in the business, barely lasted a few days as Aragorn. When the director realized Townsend was too young to play the Strider, he quickly cast Viggo Mortenson, who delivered a truly legendary performance.

To replace the talent that is Heath Ledger, three actors had to portray the character of Tony in The Imaginarium of Doctor Parnassus. With Heath Ledger passing away, leaving a part of the movie unfilmed, Depp, Farrell, and Law portrayed Tony in a way that highlights the story. Ultimately, the movie is a tribute to Heath Ledger.

Sylvester Stallone sought to change the screenplay when he got chosen to play Axel Foley. His character would have had more heroism, making Alex a legitimate action hero. The perspective was dismissed, and Eddie Murphy, who gave the movie its distinct charm, took Stallone's place.

Marty McFly wouldn't be the iconic character without the involvement of Michael J. Fox. Because of scheduling conflicts, Eric Stoltz got cast as Marty. However, his portrayal of the character and overall bad comedic timing was not quite what director Robert Zemeckis was looking for, and he effectively got recast.

The Wolverine we know and love today is usually the one portrayed by Jackman, but Dougray Scott, who was already pretty well-known in 1999, was slated to play the gruff hero. Hugh Jackman got the part when Scott's other movie took longer than expected to finish, and the rest, as they say, is history.

Johnny Depp seems like a natural fit for the wizarding world of Harry Potter, so it was only natural that fans were happy with his casting. Sadly, when the Depp-Heard scandal hit society, he was practically fired, and Mads Mikkelsen replaced him in the Fantastic Beasts movies. Hopefully, we will see Depp on the big screen soon.

Chris Farley, a veteran of Saturday Night Live, was recruited to voice the title character in the 1995 film Shrek. Sadly, Farley passed away in 1997. Farley's rendition got left abandoned in favor of fellow SNL veteran Mike Myers. Myers insisted on using his distinctive Scottish accent for the role.

Terrence Howard, James Rhodes in Iron Man, is not a stranger to rumors and controversies. Legends are that Howard got fired for multiple reasons — poor performance and salary disputes being some of them. Don Cheadle came to replace Howard and give a face to the War Machine character.

Hugo Weaving portrayed an excellent Red Skull, so it was only natural for the Marvel executives to try and get him for several movies. Because of monetary problems, Weaving couldn't portray the character for Infinity War, and Ross Marquand came to replace him. A professional voice impressionist, Marquand copied Weaving in almost every aspect.

Sometimes, even an A-list actor is not worth keeping around. While Mark Ruffalo might be the face of the modern Hulk, Edward Norton was the second to play it in the 21st century. Luckily, the Hulk got recast when Marvel started to look for a more group-friendly face. In their crosshairs came Ruffalo, the original first choice for Hulk.

In the original movie, Jennifer was seen only at the start and at the end, and Claudia Wells got the role. When it came time to film the sequel, Wells did not reprise her acting role due to family problems. Forced to recast the role, Elisabeth Shue auditioned and got the part of Jennifer.

Christopher Nolan wanted Katie Holmes to portray Rachel Dawes for both Batman movies, but because of scheduling and personal problems, she had to refuse it. Maggie Gyllenhaal replaced Holmes and acted in one of the best Batman movies ever. The good thing is that there are no hard feelings on all sides.

In Game of Thrones, The Mountain is a character who has been played by a lot of actors. Conan Stevens portrayed him in season one due to his physical characteristics. Ian Whyte then took up the role, becoming him for season two, before getting replaced by Hafþór Júlíus Björnsson. He seems to fit the description almost point to point.

Colin Firth was the original voice of the adorable bear. Firth willingly left the movie as it became clear to all parties involved that his voice was not the right one for the part. Without Ben Whishaw's unique demeanor, which he imparts to the two flawless movies, it is difficult to conceive the marmalade master.

Richard York had a severe back ailment from an incident in 1959 that he got while working a set. In 1969, when Daddy Does His Thing was under production, Richard passed out and was taken to the hospital. Shortly after, Richard Sargent got cast in the show, and left the show shortly after.

Game of Thrones is not a stranger to recasting minor characters. One of the most visible ones is Daario Naharis. Ed Skrein was the original actor to portray the mercenary, but because of political reasons and (more likely) the wish to act in a Transporter movie, he had to leave the series. Michiel Huisman replaced the actor for the rest of the seasons.

In the Frasers’ trilogy of Mummy movies, the character of Evie was played by Rachel Weisz for the first two movies and Maria Bello for the third one. Weisz had problems with the third movie's script and decided to leave the role behind — Bello came to replace her .

Anita Barone portrayed Carol in Friends for one episode, The One With The Sonogram At The End. Because Barone wanted a more vital role in the series, she left the project, and Jane Sibbett came to replace her. Friends' general popularity, even with a small screen time, was enough to make Jane Sibbett a vital part of the series.

The role of Dickon Tarly seems to have suited both of the actors portraying him very well. Knowing that it wouldn't be a recurring role, Freddie committed to Time After Time. Tom Hopper replaced him and admitted that the Dickon Tarly role secured him an acting job in the Umbrella Academy series.