Chris Hemsworth's dedication to building the physique of a Norse god almost delayed the filming of Thor when his muscles grew too big to fit into his costumes.

For the newly published book The Story of Marvel Studios: The Making of the Marvel Cinematic Universe, authors Tara Bennett and Paul Terry spoke to costume designer Alexandra Byrne, who revealed that the production schedule for 2011's Thor was jeopardized by its own star. Hemsworth had been cast to play Marvel's God of Thunder for the very first time and to prepare for the physical demands of the role, the actor exercised relentlessly before filming began, so much so that he outgrew his initial costuming measurements. With Thor's costumes unable to fit its star, the movie's production would have required a delay if not for the swift, last-minute costume alterations from Byrne and her costuming team.

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In the early stages of Thor's preproduction, Byrne took Hemsworth's measurements to start crafting his first Thor outfits. However, when Hemsworth returned to Byrne for his costume fitting, his muscles had grown so large that they were literally bursting out of his clothes. With production beginning in a matter of days, Byrne called Marvel Studios president Kevin Feige in a panic and explained that the team likely wouldn't be able to adjust his costume in time.

Ultimately, though, Byrne and the rest of the costuming department pulled together, and they got the job done. The team quickly augmented each and every one of the character's costumes to adjust to the actor's new size, fixing the costumes with only moments to spare before day one of production began. Thanks to the hard work of the crew, filming began as scheduled, with no delays required.

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Ironically, the costuming department initially feared the exact opposite scenario. At one point during pre-production, Byrne and company feared that Hemsworth wouldn't be muscular enough to fill the costume, with Byrne admitting "We thought at one stage, we'd need a muscle suit. You know, to make him bigger."

Comprised of over 500 pages across two volumes, The Story of Marvel Studios: The Making of the Marvel Cinematic Universe includes interviews with the actors, directors, producers and crew members responsible for the development of the highest-grossing movie franchise of all time. The vast compendium unveiled a host of additional trivia behind 2011's Thor, including the story of how the role of Odin stopped Anthony Hopkins from quitting acting and the reason why Marvel rejected Hemsworth's first audition tape for the movie.

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Source: The Story of Marvel Studios: The Making of the Marvel Cinematic Universe