One of the nice things about Guardians of the Galaxy is that it’s only lightly connected to the rest of the Marvel universe, and its galactic setting means things can get far, far weirder. It’s perfect for introducing some of Marvel’s more oddball concepts, like, for example, a giant head that eats planets.
No, really, that’s a Marvel villain. He’s called Ego, the Living Planet, and James Gunn is supposedly working him into the script. Ego was one of the stranger Thor villains, a scientist who somehow merged with a planet and began eating everything in his way. He’s such a menace that Galactus, the guy who eats worlds as his job, strapped a rocket engine to Ego’s backside and sent him jetting through the universe. That said, he’s something of a side character, usually only brought out when somebody needs a galactic menace or when Marvel editorial wants to take a potshot or two.
Ego is unlikely to be the main antagonist. He’s a bit too undeveloped, as a villain, and presumably the team needs somebody a bit easier to film to fight. But it’s nice to see that with the Marvel movies, everything is on the table. Now, when is Iron Man fighting Fin Fang Foom, and can it be the version of Foom obsessed with putting people in his pants