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The Truth Behind Thor's 'I Knew It' Line In Endgame

With just three words, Chris Hemsworth's Thor spoke for us all in Avengers: Endgame

When Chris Evans' Captain America picked up Thor's hammer Mjolnir in the battle scene at the end of the movie, the God of Thunder looked up and uttered, "I knew it!" What he knew, of course, was that Captain America was worthy to lift the hammer that bears the inscription, "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor."

It was one of the most powerful scenes in a film filled with them, with Thor's tiny trio of words packing a huge emotional wallop to make Cap's long-awaited Mjolnir moment even more satisfying. But the exchange didn't always play out as fans saw it on screen. 

In Slashfilm's extensive, definitive oral history of Avengers: Endgame's final battle, the creative powers behind the film revealed the truth about Thor's "I knew it!" line. Endgame editor Jeff Ford and co-writer Christopher Markus detailed what Thor was thinking in that scene, and explained that it actually took "a bunch" of takes with Hemsworth before directors Joe and Anthony Russo found the line that struck the right tone and spoke for how the audience felt in that moment. And, as it turns out, all of that happened during reshoots.

"It was during a reshoot that we shot a bunch of lines from Thor for what he would say, but the best one was, 'I knew it,'" Ford told Slashfilm. "We had [Hemsworth] on that rock and we were like, 'Say this, and this, now this.' He had to catch a flight. We had one day where we had to get a lot of Hemsworth. We were sharing him with another show and it was a reshoot thing."

Captain America's big moment with Mjolnir was planned out early in the creative process for Avengers: Endgame, but Thor's reaction wasn't. Filmmakers struggled to get it just right, with Markus revealing that Thor's "I knew it!" underwent many rounds of tweaking. Different emotions and different intonations lent to the line different meanings, and the Endgame team put Hemsworth through a pretty intense day of filming, working against the clock and the actor's strict deadline, to really nail it. 

"They might have all been 'I knew it,' just with different spins," noted Markus. "The one that's in the script is happy. I'm sure there was some jealousy, some resentment, some shock — it's such a happy moment for the audience that I'm glad we went with the happy one for Thor, because he's sort of the voice of the audience going, 'F*** yes!'"

Thor's "I knew it!" also served another purpose: to break up the high-stakes intensity of the climactic battle against Thanos with some genuine feel-good emotion. As Ford explained, "It's a great reversal in that fight, too, and we needed it there. I think it's a great way to set that off."

Why is Captain America able to pick up Mjolnir?

According to Avengers: Endgame co-writer Stephen McFeely, the Marvel crew knew as early as the summer of 2015 that they wanted to have Captain America wield Mjolnir at some point in the film, but they didn't exactly have the logic of the big moment planned out in advance. McFeely told Slashfilm that there were several ways to execute it, with Markus further noting that debate and discussion about the moment heated up around the time Thor: Ragnarok was underway.

"[Ragnarok] establishes that Thor can summon the lightning without the hammer. I think Odin even says, 'It was never the hammer.' And yet Cap summons the lightning with the hammer. You get to those things and you're like, 'It's too awesome not to do it! We'll talk about it later,'" Markus said — though it's been noted by several outlets that Cap summoning lightning while calling upon Mjolnir isn't a plot hole given the enchantment Odin place upon the hammer in 2011's Thor. Since the wielder of Mjolnir receives the powers of Thor, it's not surprising that Cap can wield lightning as well. 

As fans recall, Captain America attempted to pick up Mjolnir in 2015's Avengers: Age of Ultron, but only shifted the hammer slightly — much to the relief of Thor, who presumably feared public embarrassment if the Star-Spangled Avenger suddenly started swinging the hammer around. Like Thor's "I knew it!" line in Endgame, Cap's ties to Mjolnir changed over time. 

During an appearance on Josh Horowitz's Happy Sad Confused podcast (via Nerdist), Endgame co-director Anthony Russo explained that Marvel creatives always understood that Captain America was worthy of wielding Mjolnir, and that the character himself realized that during Avengers: Age of Ultron when he and his fellow Avengers were having a Sword in the Stone-style trial to lift the mystical hammer. Being the good guy that he is, Cap actually chose not to pick up Mjolnir, as he didn't want to hurt Thor's pride. 

As Russo tells it, "In our heads he was able to wield it, and he didn't know that until that moment in Ultron when he tried to pick it up. But Cap's sense of character and his sense of humility, sort of out of deference to Thor's ego, you know Cap in that moment realizing he can move the hammer decides not to."

It seems that Avengers: Age of Ultron director Joss Whedon agrees with that idea, as he once told a fan who asked why Cap wasn't worthy: "Did he fail, or did he stop?"

The folks at Collider have posited another theory about Cap and Mjolnir: the hero may have become worthy of wielding the hammer due to the events of Captain America: Civil War. It also seems possible that the loss of a number of his friends and teammates and the fallout from Thanos (Josh Brolin) documented in Infinity War and Endgame could have changed Cap, making him more worthy.

Regardless of when Captain America became worthy, Avengers: Endgame editor Ford said the moment when he picks up the hammer had more impact because it happened late in the Marvel film franchise: "I think seeing that realized is one of the pleasures of a long series like this, where you've really been with these characters for a long time, so when that happens, it's not satisfying unless you buy it, and I buy it."

Just like Thor, the audience was cheering for Captain America in that moment. Not only was he saving Thor from Thanos, who was on the brink of offing the God of Thunder before Cap summoned Mjolnir, but he was also joining an elite group of the worthy — a man among mostly gods. Like Ford said, "Cap is that guy."