WARNING: The following contains spoilers for "Crisis on Infinite Earths, Part 3," which premiered Tuesday on The CW.

In only three episodes, The CW's "Crisis on Infinite Earths" delivered everything from a fleeting cameo by DC Universe's Titans to Kevin Conroy's more substantial role as a murderous Bruce Wayne. However, among the Arrowverse crossover's biggest surprises arrived in the third installment, with an appearance by Tom Ellis as Lucifer Morningstar, on the appropriately named Earth-666.

The cameo not only allowed the Lucifer star to appear alongside such character as John Constantine, it also confirmed the Netflix series is part of the Arrowverse. However, there's an even larger implication, because the episode retroactively alters the first four seasons of Lucifer.

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Ellis revealed in a recent interview where in the Lucifer timeline his "Crisis on Infinite Earths" appearance fits. "We’re playing it as if it’s in the five years before the show, Lucifer, started, so when Lucifer spent five years in LA before meeting the detective and all those things unfolding," the actor said. Therefore, his appearance in "Part 3" predates any of the events of Lucifer's first season.

That means Lucifer has always been set in a post-Crisis reality. While we don't yet know what will happen in the crossover's conclusion, set to air in January as part of Arrow and DC's Legends of Tomorrow, we can certainly deduce the superheroes will save reality, in some form. The big question is, will they be able to restore the Multiverse, or will the event end with the creation of New Earth, as it did in the comics? If it's the latter, then Lucifer has been set on the Arrowverse's main Earth all along.

If, however, the heroes restore the Multiverse, then Lucifer is still on his Earth-666, only in a post-Crisis reality. Whatever the case may be, the confirmation that Lucifer is in the Arrowverse fold changes everything about the series.

Now re-watch the show from the beginning, and wonder where the other heroes of the Arrowverse are, given that the Prince of Hell now shares the same world as them -- or, perhaps, he always did.

"Crisis on Infinite Earths" will return after the winter hiatus. The crossover will conclude on Tuesday, Jan. 14 in Arrow at 8 p.m. ET/PT and in DC's Legends of Tomorrow at 9 p.m. ET/PT. Lucifer is availble to stream now on Netflix. The series' fifth and final season will arrive sometime in 2020.

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