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

While the major events of Part 1 of "Crisis on Infinite Earths" have already changed Supergirl and Arrow in big ways, it’s also having an effect on other shows. In particular, one subplot from the episode has cast the premise of Legends of Tomorrow in a completely different light.

After Clark Kent and Lois Lane send Jonathan Kent off in a pod to escape the destruction of Argo, Brainy tracks their infant son through a temporal wormhole. It's revealed Jonathan ended up in Star City in 2046, which Ray Palmer and Sara Lance immediately recognize, as they’ve been there before. It turns out the bad future from Legends of Tomorrow Season 1 episode “Star City 2046” is Earth-16 (so named because the show premiered in 2016). There, they meet an older Oliver Queen, who found Jonathan’s pod and took him back to the bunker to keep him safe.

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The actual storyline is short and relatively simple: Lois finds Jonathan and Oliver fights the intruders before recognizing Sara. On this Earth, Sara didn’t survive the Queen’s Gambit sinking, so this Oliver is seeing her for the first time in 40 years. We also learn that this Oliver is hilariously unfamiliar with the multiverse. As Oliver and Sara say goodbye, she reassures him that he’s not at fault for her death, and our characters get out just before the anti-matter wave destroys Earth-16.

The logic of the multiverse definitely informs this retcon. In the intro to the first episode of "Crisis on Infinite Earths," the Monitor talks about the multiverse being “every existence multiplied by possibility.” This matches up with the explanation given of the multiverse on The Flash, where new Earths are created for each possible decision someone could have made.

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Taken too literally, this would make the multiverse incredibly vast due to the number of decisions made by every person every day. Still, it fits Legends of Tomorrow quite well: their alternate timelines would be how new Earths get created. Time goes one way originally, something changes to make an alternate universe, then they fix time for their Earth while the other continues on as another Earth in the multiverse.

Rip Hunter even called this out when the team first visited Star City in 2046. He called it a possible future that they could prevent by making changes in the past. They made those changes, but apparently that version of Star City 2046 went on as an alternate Earth until its destruction in this episode.

This opens up a huge number of possibilities to revisit some of the alternate timelines that came up on Legends. Does Doomworld still exist in some alternate Earth? What about that mission we never saw where Napoleon used ABBA to conquer Europe? A revisit to the world with Beebo Day? The possibilities are endless.

One episode in and Crisis is already rewriting what we thought we knew about the Arrowverse. Even in the smaller plotlines, it’s opening up big possibilities for the future – assuming any of those Earths survive the Crisis, of course. That’s far from a guarantee, given what we’ve already seen. If any survive, however, it gives Legends some more toys they can play with in Season 5.

"Crisis on Infinite Earths" continues in Batwoman on Monday, Dec. 9 at 8 p.m. ET/PT and 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.

KEEP READING: Crisis on Infinite Earths Is a ‘Prequel’ to Legends' Fifth Season