The third Thor film only hit theaters stateside last weekend, yet the film has already grossed an impressive $500 million at the worldwide box office and helped propel the Marvel Cinematic Universe past $5 billion. However, while Thor: Ragnarok continues to smash box expectations -- with the film set to take in another $61 million this weekend -- it's easy to forget that the Marvel Cinematic Universe wasn't always set to be a blockbuster success. In fact, according to Thor director Kenneth Branagh, it was very much sink or swim in the beginning especially when it came to introducing the God of Thunder, a character that proved to be tonally difficult to capture.

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While promoting his latest film, Murder on the Orient Express, Uproxx spoke to Branagh about directing the first Thor movie, which was set to follow on the heels of Iron Man, a smashing success, and The Incredible Hulk, a film that didn't work as well as Marvel had hoped. According to Branagh, at that point, it was still a huge risk for the MCU, and the success of Thor played a vital part in whether they'd move forward with their original overarching, interconnected plan.

When asked if the operation would have fallen apart if the first Thor movie didn't work, Branagh revealed that was essentially how they all felt. Not only did they have the task of introducing a brand new character, but they also had to successfully capture a new tonal direction in this cinematic universe, which proved to be a daunting task in itself.

No question that Kevin Feige used to say to me, “This is the single most difficult tonal challenge for us, to make this movie work in itself and fit into this large universe.” In fact, I think Thor, and in Chris Hemsworth’s performance, becomes an absolutely integral part.

Thankfully, they managed to overcome the tonal challenges, for the most part. While the Thor franchise has seen its complaints -- mainly with Thor: The Dark World -- there's no denying that Branagh and company managed to successfully introduce the God of Thunder to a wider audience.

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In theaters now, director Taika Waititi’s Thor: Ragnarok stars Chris Hemsworth as Thor, Mark Ruffalo as Hulk, Tessa Thompson as Valkyrie, Tom Hiddleston as Loki, Cate Blanchett as Hela, Jeff Goldblum as The Grandmaster, Idris Elba as Heimdall, Anthony Hopkins as Odin, and Karl Urban as Skurge.