WARNING: The following contains major spoilers for “Crisis on Infinite Earths, Part 2,” which aired Monday on The CW.

While the CW's "Crisis on Infinite Earths" has been filled with cameos from actors and characters from old DC Comics movies and shows, Michael Rosenbaum has not reprised his Smallville role as Lex Luthor. While Rosenbaum reportedly turned down a role in the crossover earlier this year,  his version of Lex still gets a mention that references a major piece of Smallville continuity that was never shown in detail on the show.

While traveling through the multiverse for a version of Superman who's destined to be a pivotal figure in "Crisis," Earth-38’s Superman and Lois Lane and Earth-1 Iris West-Allen end up on a version of the Kent farm where they find Earth-167’s Clark Kent, portrayed by Tom Welling. The Arrowverse heroes try to warn Smallville's Clark that Earth-38 Lex Luthor is going on a Superman-hunting spree with the all-powerful Book of Destiny. In response to that revelation, Clark simply says, “I didn’t know the President was in town.”

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While this draws confused looks from Iris, Lois, and Superman before Earth-38 Lex zaps them off to another Earth, this quietly confirms that Lex Luthor eventually became the President of the United States in the world of Smallville.

The idea of Luthor becoming the U.S. President isn't anything new. Luthor was elected U.S. President in the comic book DC Universe in 2000, shortly before Smallville premiered. Early in its run, Smallville acknowledged this then=ongoing storyline in its sixth episode. When a young Lex visits an old seer, Lex is given visions of his future, including one where he's wearing a bright white suit in the White House’s Oval Office. This puts the idea of becoming the President in his head, which he pursues later in the series.

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President Lex Luthor Smallville

While we don’t actually see too much of Lex as president, the show continued to tease the idea throughout the rest of its run. In Season 9, Episode 21, “Salvation”, Clark has a vision of the future that showed Lex announcing his run for President in 2013. The series finale eventually confirms this, with a news broadcast from the flash-forward to 2018 showing Lex having been elected president.

This general timeframe also points to Earth-167 being on roughly the same timeline as Earth-1, as the Crisis is happening on December 10, 2019, according to what the Monitor has said on The Flash. This would put Lex roughly a year into his first term as president, though why he’s elected president in a year that should be a midterm election is something viewers are left to puzzle over.

This reference even keeps with the continuity of the Smallville Season Eleven comics. Lex gets into politics in the comics, taking a role as the liaison between the president and the Justice League, with his eyes on the top office himself. The comics never actually depicted his election, but it’s the logical extension of where he ended the comics and his ambition for power.

Even though contractual negotiations seem to have kept us from getting an appearance by Michael Rosenbaum, his Lex is still present in the background of Crisis. Since Clark gave up his powers to raise a family with Lois on his family farm in this universe, it seems like Smallville's Superman and Lex Luthor both ended up getting the happy endings they wanted.

"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.

NEXT: Crisis Gives Tom Welling’s Clark Kent the Farewell He Deserves