SPOILER WARNING: This article contains major spoilers for "Crisis on Infinite Earths, Part 2," the second installment of this year's Arrowverse crossover.

The second chapter of "Crisis on Infinite Earths" delivered another reference to DC's Guardians of the Galaxy, in the form of the Guardians.

The Arrowverse heroes are still reeling after the death of the Green Arrow, Oliver Queen, in the first chapter of The CW crossover. While sharing a drink to honor Oliver, The Monitor appears to fill the heroes in on the next stage of their mission. Part of his speech involves the mention of the Tome of the Guardians and the Book of Destiny, which could be a reference to the Green Lanterns' Guardians of the Universe.

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There have been vague references to the Green Lanterns during the existence of the Arrowverse, with the biggest nods associated with Arrow's John Diggle, played by David Ramsey. Fans have long speculated that Diggle could be the Green Lantern John Stewart of the Arrowverse. Ramsey previously revealed the final season of Arrow will address the Green Lantern theories.

"Crisis on Infinite Earths" continues in The Flash on Tuesday, Dec. 10 at 8 p.m. ET/PT. 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.

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