One of the things that has helped make the MCU so successful is its ability to cast these iconic roles very effectively. From the heroes to the villains to the memorable side characters, the filmmaking teams behind these superhero adventures have a talent for finding the right fit between character and actor.
Of course, casting doesn't always work out as neatly as intended which has led to some noticeable instances of recasting in the movies. Whether because of scheduling conflicts, character needs, or creative differences, these MCU roles had to undergo some changes.
Thanos
Thanos was a looming threat over much of the MCU before The Avengers. Following Loki's defeat on Earth, Thanos is briefly seen grinning at the prospect of taking on these heroes in the future.
Interestingly, unlike his later appearance, Thanos was a practical creation played by Damion Poitier. When reintroduced in Guardians of the Galaxy, Thanos was played by Josh Brolin in a motion-capture performance. Given the expanded and important role Thanos was to play going forward, it makes sense that the role was changed to a more established actor and the CGI take on the character proved very effective.
Howard Stark
Like Thanos, Howard Stark was first shown in the MCU in a wordless appearance only to be recast when the role expanded later on. In the first Iron Man, Tony's father was seen in photos showing his amazing career and his partnership with Obadiah Stane. Though it is a brief appearance, actor Gerard Sanders looked the part as Howard Stark in these images.
While Dominic Cooper would take on the role of younger Howard Stark in Captain America: Civil War, and Avengers: Endgame.
Fandral
The Warriors Three always seemed like a bit of a Thor.
When it came time for Thor: Ragnarok.
Red Skull
Given that Red Skull is probably Captain America's most famous enemy from the comics, fans likely expected that he would play a larger role in the MCU than he did. He was appropriately introduced in Captain America's first solo movie, played memorably by Hugo Weaving. But after getting sucked up into the cosmos by the Tesseract, Red Skull disappeared from the MCU.
In the years following Captain America: The First Avenger, Weaving spoke publicly about not liking the role and not being interested in returning, which made it seem unlikely the character would be seen again. However, Red Skull made a surprise appearance in Avengers: Infinity War as the keeper of the Soul Stone. Unsurprisingly, Weaving didn't return for the cameo but was recast with Ross Marquand doing a convincing Hugo Weaving impression.
Cassie Lang
Cassie Lang was first seen as the adorable young daughter of Scott Lang in the Ant-Man movies. However, the character was aged up following the Blip which meant that the role needed to be recast with an older actor. In Avengers: Endgame, Emma Fuhrmann appeared as the older Cassie Lang as she reunited with her father after not seeing him in five years.
However, when confirmed that the character would return in Ant-Man and the Wasp: Quantumania it was announced that the role would now be played by Kathryn Newton. Newton is an star in Hollywood and given that Cassie Lang might be becoming a superhero herself, it's not surprising that Marvel looked for a recognizable actor to take over the role.
James 'Rhodey' Rhodes
James 'Rhodey' Rhodes was introduced as Tony Stark's best friend in the first Iron Man movie with Terrence Howard delivering an enjoyable performance in the buddy role. He even got to tease the future of War Machine as he sees the silver armor and promises, "next time baby". As it turns out, Rhodey predicted that correctly, except it would be a new actor donning the armor.
With reports of demands for a raise and unhonored contracts, Howard did not return for Iron Man 2. Instead, Don Cheadle took over the role and quickly established a fun chemistry with Robert Downey Jr's Tony Stark. And although Tony is gone, Rhodey remains a part of the MCU, including his own solo series with the Armor Wars.
Bruce Banner
Given how successful the MCU has been, it is strange to think that there was ever uncertainty about if it would work out. But with one of the main heroes being recast before they ever reached The Avengers, it added to the thought that this whole thing might be a bad idea.
Indeed, The Incredible Hulk established Bruce Banner as the second of the MCU's heroes, debuting just after Iron Man's first solo adventure. Edward Norton played the role in the darker story. However, Norton's unhappiness over the finished project and a desire to do other things led to Mark Ruffalo taking the role. As dramatic as the recasting was, Ruffalo soon became a fan favorite and an integral part of the MCU.
