Crisis on Infinite Earths is not only uniting various DC TV shows from the past but also bringing together the entire Arrowverse, but there actually aren't too many episodes that viewers need to watch beforehand. Given how many shows and episodes there are in the Arrowverse, it may be daunting for newcomers or those who have simply fallen behind to catch up before Crisis, but it really shouldn't be too difficult to do so.
Since the first crossover special between Arrow and The Flash six years ago, the annual team-ups between the superhero shows on The CW have become highly anticipated events. Yet none of these events have become quite so eagerly awaited as Crisis on Infinite Earths. This is partly due to how the Arrowverse has been teasing this event for years, since the first episode of The Flash. It is also due to how the coming Crisis has enveloped the whole of DC Comics' television offerings, with Smallville and the 2002 Birds of Prey series having been absorbed into the Arrowverse.
Thankfully, all of the episodes that directly lead into Crisis on Infinite Earths were released within the past year and are now available for streaming on Netflix. Many of these episodes are also, at the time of this writing, available for streaming for free through The CW website and app. Of course, it's good to keep up with the latest seasons of each show as well, as they will all lead directly into Crisis on Infinite Earths.
Elseworlds
- The Flash, Season 5, Episode 9, "Elseworlds - Part 1"
- Arrow, Season 7, Episode 9, "Elseworlds - Part 2"
- Supergirl, Season 4, Episode 9, "Elseworlds - Part 3"
The road to Crisis on Infinite Earths began with Elseworlds - the Arrowverse's 2018 crossover event. Spread across three nights and the midseason finales of The Flash, Arrow and Supergirl, the story focused upon a cosmic being called The Monitor and his efforts to test the heroes of various realities. For the heroes of Earth-1, this test came in the form of the Book Of Destiny - an artifact capable of rewriting reality, which was placed in the hands of the mentally unstable John Deegan.
Alerted to the danger Deegan posed after his meddling with the book caused Oliver Queen and Barry Allen to trade powers and lives, ala Freaky Friday, the two heroes traveled to Earth-38 and secured the help of Kara Zor-El and her cousin, Superman, in restoring order to Earth-1. Along the way, they made the acquaintance of Batwoman - a new vigilante who had taken up the task of protecting Gotham City after the mysterious disappearance of Batman several years earlier.
Apart from introducing the Monitor and explaining his motivations for testing the heroes of multiple Earths so that he can find a worthy army capable of averting "a great crisis", these episodes also introduced the Earth-38 version of Lois Lane. Elseworlds also acted as a prequel to the upcoming Batwoman series, bringing the character of Kate Kane into the Arrowverse. Finally, these episodes set up a major subplot that tied into the Arrow season 7 finale.
Supergirl
- Supergirl, Season 4, Episode 15, "O Brother, Where Art Thou?"
- Supergirl, Season 4, Episode 16, "The House of L"
- Supergirl, Season 4, Episode 22, "The Quest For Peace"
Supergirl season 4 saw the Girl of Steel facing new enemies, both foreign and domestic. On the home-front, she had to contend with the Children of Liberty - an anti-alien militia group, who blamed immigrants from other planets for all manner of social ills. From overseas came the Red Daughter; a clone of Supergirl raised to hate America and trained to lead the communist nation of Kazina in a war against the United States. Ultimately, all these threats were revealed to be the work of one man - Lex Luthor.
Luthor's convoluted scheme was unveiled over the course of 3 episodes, including Supergirl's season 4 finale, "The Quest For Peace". While Luthor died as a result of his treachery, his story is not yet over. The finale showed the Monitor arriving at the secret lair where Lex's corpse was abandoned and it was suggested that he somehow arranged for Luthor's resurrection. The episode also revealed Malefic, the evil brother of the Martian Manhunter J'onn J'onzz, being transported to Earth by the Monitor. The Monitor's reasons for helping the two villains have yet to be explained.
Arrow
- Arrow, Season 7, Episode 16, "Star City 2040"
- Arrow, Season 7, Episode 22, "You Have Saved The City"
The story of Arrow season 7 was split between two time periods. In the present day, Oliver Queen and his allies fought to save Star City from a secretive criminal syndicate known as the Ninth Circle, which had come to be controlled by Oliver's half-sister from one of his father's affairs. In the future of Star City 2040, the next generation of heroes, including Oliver Queen's son William Clayton and his daughter, Mia Smoak, fought their own battle to save Star City from a terrorist group known as The Eden Corps.
While both groups of heroes were successful in saving Star City, Oliver and his wife, Felicity Smoak, were forced into hiding so that a pregnant Felicity could give birth safely after they both wound up on the hit-list of the Ninth Circle. Shortly after Mia's birth, it was revealed that Oliver had made a bargain with the Monitor during the events of Elseworlds that required he abandon his family to assist the Monitor with finding the heroes he needed for the coming battle. The flash-forwards to 2040 ended on a similar note, with a middle-aged Felicity Smoak biding her daughter and adopted son farewell, shortly before meeting the Monitor regarding her own bargain with the cosmic being.
The Flash
- The Flash, Season 5, Episode 18, "Godspeed"
- The Flash, Season 5, Episode 22, "Legacy"
The Flash season 5 centered around Team Flash's battle with a new villain called Cicada. They were assisted by an unexpected ally; Nora West-Allen, Barry and Iris' daughter from the year 2049. Armed with her father's powers and an encyclopedic knowledge of her The Flash's future battles, Nora proved her worth several times, though she seemed to be keeping secrets from the rest of the team. Eventually, it was revealed why Nora didn't want to discuss the details of her training in the future; she had been taught how to access the Speed Force by her father's worst enemy, the Reverse-Flash, Eobard Thawne, who was imprisoned in her time.
The season 5 finale, "Legacy," revealed that Thawne had trained Nora as part of a scheme that would indirectly bring about his freedom in the future. It also had the unfortunate side-effect of removing Nora (or at least, this version of her) from the timeline; a consequence for which Thawne surprisingly showed remorse, though he still taunted Barry by saying that he would see him "in our next crisis." The episode concluded with the revelation that the newspaper from the future predicting Crisis on Infinite Earths (which first appeared in The Flash's pilot episode) had changed, with the date of the Crisis on Infinite Earths moving up from April 2024 to sometime in 2019.
Legends Of Tomorrow
- Legends of Tomorrow, Season 4, Episode 16, "Hey, World!"
Legends of Tomorrow season 4 saw the titular team of time travelers wandering the time stream in search of Fugitives - magical creatures accidentally freed from an inter-dimensional prison plane. The team's ranks swelled, as enemies like the sorceress Nora Darhk became allies. At the same time, the team's allies were seduced by the power of the demon lord Neron, who sought to use the Fugitives for his own evil plans to build his power by playing on mortals' fear of the strange and unusual.
As was typical in previous seasons, Legends of Tomorrow's story was largely removed from the Arrowverse at large. The team did not take part in the events of Elseworlds and were similarly ignored when they called Supergirl, Flash, and Green Arrow to ask for help with their plan to combat Neron's fear with the joy and wonder inspired by a monster-themed amusement park. The Monitor had a brief cameo amid the insanity of this battle, being seen in the crowd of spectators enjoying a bag of popcorn. The events of the episode may prove important to the story of Crisis on Infinite Earths, however, as one Legend sacrificed themselves to save a teammate, only to be replaced by an alternate incarnation from a revised timeline. This fate befell many characters from redundant timelines in the original Crisis on Infinite Earths storyline in the comics.