WARNING: The following article contains spoilers for "Hey, World!," the Season 4 finale of DC's Legends of Tomorrow.
Just like The CW's other Arrowverse series, the season finale of DC's Legends of Tomorrow contains a tease for this fall's "Crisis on Infinite Earths" crossover.
Toward the end of the episode, the Monitor, all-knowing cosmic being who was behind the machinations of last season's "Elseworlds," is show in the audiences as the Legends perform at Heyworld. Their goal is to teach people that magical creatures aren't anything to be afraid of. So they create Heyworld, a theme park in which they perform to showcase how harmless these scary-looking beings are.
The performance unfolds as The Monitor looks on from the stands, and snacks on popcorn. He doesn't look especially pleased with the development.
The Monitor's appearance on the Arrowverse shows -- some seemingly random, and others a little more purposeful -- are an homage of sorts to DC's original Crisis on Infinite Earths. In the build-up to the 1985 comic book crossover, the character made appearances across the publishing line, beginning in 1982 in The New Teen Titans #21.
Why would The Monitor be at all invested in the Legends' zany plan? Well, the Legends are fundamentally changing events through their actions. Their goal is to thwart the demon Neron, who's using the fear of magical creatures to power the return to Earth of the denizens of Hell. If people aren't afraid of those creatures, the Legends reason, Neron's plan won't come to fruition.
Yet, there are other serious consequences to their actions, the biggest being the fate of Zari, who possesses the Air Totem. She's born much later in the timeline than most of the other Legends, and her family is torn apart by an anti-meta act passed in the future. The fear of metas and magical creatures led to the death of Zari's brother, who previously possessed the Air Totem. By changing the timeline, the Legends change Zari's fate: Her brother doesn't die, and she will never receive the Air Totem.
In order to keep Zari's memories intact, the Legends leave her on the Waverider, where she's protected from the timeline revisions. But when Nate Heywood, whom she recently began dating, dies, she leaves the ship to try to save him. Zari succeeds, but in the final moments of the finale, Zari is replaced by her brother as a Legend. No one remembers Zari, and her brother is an accepted member of the team.
Could Zari have been a key player in something related to the coming "Crisis on Infinite Earths"? Will her brother not be a suitable substitute? It's difficult to say, but The Monitor's reaction in the Legends season finale indicates that could very well be the case.
DC’s Legends of Tomorrow stars Caity Lotz, Dominic Purcell, Brandon Routh, Nick Zano, Maisie Richardson-Sellers, Tala Ashe, Matt Ryan, Jes Macallan and Courtney Ford. The series will return at midseason 2020 on The CW.