Thor: Ragnarok provided clues for the introduction of Smart Hulk (Mark Ruffalo) in Avengers: Endgame. In 2017, the God of Thunder's Marvel sub-franchise got a major revamp thanks to director Taika Waititi. Instead of the moody tone the first two Thor films had, the filmmaker made everything lighter and more humorous, resulting in a personality make-over for Thor as well. Aside from titular character, however, Ragnarok also featured another Avenger - Hulk (Mark Ruffalo), whom fans hadn't seen since he went missing at the end of Avengers: Age of Ultron.

While Captain America (Chris Evans) and Iron Man (Robert Downey Jr.) fought about the Sokovia Accords, and then Bucky Barnes (Sebastian Stan) in Captain America: Civil War, their fellow Avengers teamed up to save Asgard in Ragnarok. Granted that though Thor and Hulk's initial meeting wasn't exactly peaceful as they were pit against each other in Sakaar's Battle of the Champions, they eventually made amends and got together to save the former's homeworld.

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Aside from being Thor's third standalone film, Ragnarok also started Hulk's three-film arc which continued in Avengers: Infinity War and ended in Avengers: Endgame. This supposedly worked around the reality that Marvel Studios is unable to producer a Hulk solo project given the character's rights are still with Universal. With that, it makes sense that there's a clear progression for the character from Ragnarok until Endgame. While it may not be obvious then, looking back at the films, Waititi's film hinted at the eventual introduction of Smart Hulk.

Smart Hulk in Avengers Endgame

The most glaring clue was Hulk learning to talk in Ragnarok. By the time the green-rage monster emerged in the film, it had been two years since he was Bruce Banner. Because of this uninterrupted period of time, Hulk was able to learn to talk, even if he only managed to get to the stage of speaking like a toddler. This allowed him to communicate what he felt, albeit in broken sentences. Aside from the talking, he also acted like a small child, including the tendency to throw a tantrum once in a while. After Banner found a way to merge his consciousness with his alter-ego, Smart Hulk's most striking new ability is talking in complete sentences. In effect, Endgame's Hulk seemed to be the grown-up version of the same character in Ragnarok.

Aside from Hulk's capabilities in Ragnarok, the film also visually foreshadowed the merging of Bruce Banner and his green monster persona. After locating the Quinjet he fled in at the end of Age of Ultron, the ship triggered Hulk's memory back, resulting in his human alter-ego to emerge. Clueless about what happened in the last couple of years, he checked the craft's video surveillance footage to see how he ended up in Sakaar. While watching the video, the reflection of Banner's face merged with the Hulk’s on the video, and it stayed like that for a while. Knowing what the character's future looks like now, it's easy to see that this particular scene foreshadowed two personas melding together in Endgame as Smart Hulk.

Marvel Studios planned to debut Smart Hulk even before Avengers: Endgame. In fact, the character was supposed to make his first MCU appearance in Infinity War, but the filmmakers ultimately opted against it, saving the character's planned transformation in the next film instead. With the franchise known for playing the long game, it made sense that they sneakily planted clues for the future of Bruce Banner and Hulk in Thor: Ragnarok. The question now is whether or not they'll retrospectively show exactly how Smart Hulk was created in the five-year time-gap since the heroes' defeat to Thanos (Josh Brolin).

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