WARNING: The following contains spoilers for Eternals, now on Disney+.

The Eternals are some of the more uniquely designed characters in the Marvel Cinematic Universe, operating on a level that most other heroes aren't even aware of and nowhere near capable of taking care of on their own, but one of their most shocking threats ends up being a force of nature that audiences may have seen before. Eternals reveals that at the heart of the Earth is a cosmic force that's been building steam before it awakens -- which is a surprisingly similar plot twist to one that occurred in Steven Universe.

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Eternals reveals the existence of a Celestial Egg within the world's core. Once it has absorbed enough life from the planet, it will empower the being within and allow it to ascend to its proper place in the cosmic cosmology of the MCU. Although the act will destroy the Earth (and kill everyone and everything on the planet), the ensuing being will go on to create trillions of new lives as part of the universal cycle of life. Fearing the loss of humanity in this process, Sersi (Gemma Chan) and some -- but not all -- of the Eternals elect to try and use Druig (Barry Keoghan) and his telepathy to more or less put the Celestial to sleep and allow humanity to escape the planet before it awakens and shatters the world.

Although the Celestial Egg has been an element of the Marvel Universe for decades and appeared in multiple stories over the years, this specific imagining of the concept bears more than a few similarities with the Cluster from Steven Universe. In the animated Cartoon Network series, the Diamonds -- a race of ancient and powerful aliens -- spread their reach across the galaxy. One of their plans involves hibernating shards of various Gems (the lower race that serves at the behest of the diamonds) together at the center of the Earth, cooking it into a living weapon. Like the Celestial Egg, the ascension of the being will eradicate the world and destroy all life on the planet. And like with the Celestial Egg, the primary plot line around the Cluster becomes about finding a way to contain it.

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At the end of their respective story arcs, both beings begin to awaken,  symbolized by massive earthquakes spreading across the planet and a giant hand trying to force its way out. In Steven Universe, Steven and the rogue Gem scientist Peridot eventually find the Cluster, and Steven soothes its confusion and pain -- convincing it to sleep and spare the planet. The Cluster even eventually becomes an ally to Steven and his family, helping fight back against the Diamonds when they invade the Earth. However, the Eternals aren't so lucky. Ikaris (Richard Madden) injures Druig and prevents him from accessing the Uni-Mind to psychically force the Celestial back to sleep. Instead, it begins to rise up, and the fight takes part on its hand, prompting Sersi to seemingly kill the Celestial to save Earth.

Both cosmic beings hidden within the Earth operate differently -- and the fallout from their attempt to rise is very different. The Cluster becomes a friend, while Eternals' post-credits sequence reveals that the Celestials will now openly judge humanity (and potentially destroy the Earth anyway) after they see the history of the people through the eyes of the captured Eternals. But it's notable that both stories feature a surprisingly similar existential threat to the world that takes markedly similar imagery of a hand rising out of the Earth and bringing about the end of all things. It's an interesting coincidence, especially in terms of shared imagery.

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