Thanos has a shocking explanation for the Hulk's shape-shifting abilities
Thanos once stated that he believed there was a specific reason for the Hulk's transformation, as the Mad Titan shared his theory about the hero's different forms.
In Bruce Banner's mind, Thanos once shared his theory that humans and his Hulk form have two different souls. In Marvel Comics' Thanos vs. Hulk, the Mad Titan revealed that he believed the hero's transformation was linked to the possibility of having separate souls. Thanos confides his theory to Banner and the Hulk, saying he needs to study the Hulk more to find out what's really going on about them.
In Thanos vs. Hulk #2 by Jim Starlin, Andy Smith, Frank D'Armata, and Marvel Comics' Travis Lanham, Annihilus, the overlord of the Negative Zone, discovers an element in the Hulk that can help him with his plans to rule the galaxy. After performing experiments on him, with virtual versions of the Hulk and Bruce trapped inside Banner's mind, Thanos decided to learn more about what his cosmic counterpart was up to. After the Mad Titan linked himself to Banner's consciousness, Thanos met with Bruce and the Hulk, revealing his own theories about their transformation and having two separate souls.
Thanos' Hulk Theory Explained
Thanos encounters Bruce Banner and the Hulk in his consciousness, as he explains that because he has been shapeshifting for so long, the beast seems Develop their own independent and distinct personality. He told them that he believed they actually had two separate souls. While he didn't elaborate on his theory, nor did Banner or the Hulk confirm his theory, he revealed a phenomenon worthy of future research.
Due to the Hulk's multiple transformations in the MCU, the answer to whether he has a separate soul between Banner and the Emerald Giant is complicated. There is no doubt that Bruce's weird appearance has its own unique personality. This personality can also change, as the Hulk morphs into Joe Physit, Worldbreaker Hulk, and The Master at various points in his superhero career. However, Banner and the Hulk appear to be the same soul with multiple personalities. Although, Thanos' theory shouldn't be dismissed outright, as it would make sense for Hulk and Banner to have two separate souls, especially considering they've been separated before.
Perhaps one day, Thanos will find out whether all the transformations between Bruce Banner and the Hulk resulted in him having two separate souls. But for now, the Mad Titan's guesses are as accurate as anyone's, because there's no definitive answer yet was revealed. Still, Thanos' inquiry is another big question about the Hulk.