Guardians of the Galaxy first introduced us to the concept of Celestials in the Marvel Cinematic Universe, while the sequel revealed that Star-Lord's father, Ego the Living Planet, was one of these god-like beings. He's never been a Celestial in the comic books, and the events of Eternals further muddied the waters of whether the villain's story was true.
In Chloe Zhao's film, we learn that the Celestials are seeded in planets and then destroy those worlds when they emerge (following millions of years of feeding off its inhabitants). That doesn't really line up with what we know about Ego, something Eternals writer Kaz Firpo acknowledged in an interview with The Direct.
"We talked about it at length, but it's one of those things where I think that maybe [Guardians of the Galaxy: Vol. 3] will have something to say about it," the writer teased. "Ego's a really fascinating character, whether he's lying or not, that's a question..."
"I think that you've seen the Celestials now in our film, what they are, what they're capable of, the fact that they are truly as large as planets, give birth to suns, and they're immortal space gods -- even more than our tiny little immortal space gods," Firpo continued. "So I think it's going to be something that we're going to continue to get to explore a little bit."
Confirming the Eternals are unaware of Ego's existence, he adds: "Was he an imposter? I don't know, but I'm excited to see James Gunn's Guardians 3 as much as you are."
One possible explanation is that a seed was planted in the world that would become known as Ego, but something went wrong, and the process created little more than a brain that made the planet sentient. That would basically make the villain a Deviant Celestial, and there is a chance Guardians of the Galaxy Vol. 3 plans to address this in some way, shape, or form.
Eternals is now playing in theaters.