Ever since he first appeared in Avengers: Endgame, audiences have fallen in love with Smart Hulk. But just how were they able to pull it off? Just how did they make such a lifelike Hulk that looks so much like Mark Ruffalo? Well, a new video has your answer.

In a YouTube video published by WIRED, we get a closer look. With the help of a motion-capture suit, the filmmakers were able to put a lot of Ruffalo into the computer-generated Hulk, right down to his facial expressions.

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Ruffalo's real-life touch also helped to make the Smart Hulk come off as more proportioned and human. Even if Smart Hulk had to be both brains and brawn, the best of both worlds, he also needed to be relatable.

Added to that, the animators have already gotten used to constructing the Hulk bit by bit. They were used to his every last skin, bone, and muscle, so adding a more human appearance was just the next step.

Even though Ruffalo was needed to appear alongside the other actors on set, just to get his every detail and reaction, the animator's skills can't be underestimated either. They were so meticulous, they even needed to craft the sausages the Hulk eats out of thin air.

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Directed by Joe and Anthony Russo, Avengers: Endgame stars Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Mark Ruffalo as Bruce Banner, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Brie Larson as Captain Marvel, Paul Rudd as Ant-Man, Don Cheadle as War Machine, Karen Gillan as Nebula, Danai Gurira as Okoye and Bradley Cooper as Rocket, with Gwyneth Paltrow Pepper Potts, Jon Favreau as Happy Hogan, Benedict Wong as Wong, Tessa Thompson as Valkyrie and Josh Brolin as Thanos. The film is available on Digital HD, Blu-ray and 4K UHD.