Crisis on Infinite Earths

Crisis on Infinite Earths is the name of the sixth annual Arrowverse crossover event between, , ​​​​​, , and. Additionally, events in the episode  and a two-issue comic,, tie into the crossover. It began over three nights in December 2019 from December 8 to December 10 and concluded on January 14, 2020.

Synopsis
The "Crisis" event brings together the heroes from multiple Earths to battle against the Anti-Monitor, a godlike villain who threatens to destroy all reality.

Cast

 * Stephen Amell as Oliver Queen/Green Arrow/The Spectre and Oliver Queen/Green Arrow
 * Audrey Marie Anderson as Harbinger and Lyla Michaels
 * Brec Bassinger as Courtney Whitmore/Stargirl
 * Melissa Benoist as Kara Danvers/Supergirl
 * Katie Cassidy as Laurel Lance
 * Tom Cavanagh as Dr. Harrison Nash Wells/Pariah and Harrison Nash Wells
 * Osric Chau as Dr. Ryan Choi
 * Kevin Conroy as Bruce Wayne
 * Jon Cryer as Lex Luthor
 * Erica Durance as Alura Zor-El and Lois Lane
 * Tom Ellis as Lucifer Morningstar
 * LaMonica Garrett as Mar Novu/The Monitor and Mobius/Anti-Monitor
 * Rick Gonzalez as Rene Ramirez/Wild Dog and Rene Ramirez/Wild Dog
 * Grant Gustin as Barry Allen/The Flash
 * Reina Hardesty as Weather Witch
 * David Harewood as J'onn J'onzz/Martian Manhunter
 * Juliana Harkavy as Dinah Drake/Black Canary and Dinah Drake/Black Canary
 * Raul Herrera as Sargon the Sorcerer
 * Tyler Hoechlin as Clark Kent/Superman and Superman
 * Camrus Johnson as Luke
 * Katrina Law as
 * Chyler Leigh as Dr. Alex Danvers and Dr. Alex Danvers
 * Stephen Lobo as Jim Corrigan
 * Caity Lotz as Captain Sara Lance/White Canary
 * Jes Macallan as Ava Sharpe
 * Nicole Maines as Nia Nal/Dreamer and Nia Nal/Dreamer
 * Katie McGrath as Lena Luthor
 * Katherine McNamara as Mia Smoak/Blackstar
 * Melanie Merkosky as Xneen
 * Dina Meyer as
 * Ezra Miller as Barry Allen
 * Wentworth Miller as
 * Griffin Newman as Trivia host
 * Danielle Panabaker as Dr. Caitlin Snow/Frost and Dr. Caitlin Snow/Frost
 * Candice Patton as Iris West-Allen
 * Amanda Pays as
 * Eileen Pedde as President of the United States
 * Dominic Purcell as Mick Rory and Mick Rory/Heat Wave
 * David Ramsey as John Diggle/Spartan and John Diggle/Spartan
 * Jesse Rath as Querl Dox/Brainiac 5
 * Alan Ritchson as Earth-9 hooded vigilante
 * Ruby Rose as Kate Kane/Batwoman
 * Brandon Routh as Dr. Ray Palmer/The Atom, Clark Kent/Superman, Dr. Ray Palmer/The Atom, and Superman
 * Matt Ryan as John Constantine
 * Hartley Sawyer as Ralph Dibny/Elongated Man
 * Johnathon Schaech as Hex
 * Ashley Scott as Helena Kyle/Huntress
 * John Wesley Shipp as Barry Allen/The Flash
 * Azie Tesfai as Kelly Olsen
 * Russell Tovey as The Ray
 * Elizabeth Tulloch as Lois Lane, Lois Lane's Earth-75 doppelgänger, and Lois Lane
 * Carlos Valdes as Cisco Ramon/Vibe
 * Curran Walters as Earth-9 masked vigilante
 * Burt Ward as Earth-66 citizen
 * Tom Welling as Clark Kent
 * Wil Wheaton as Earth-38 doomsday protestor
 * Cress Williams as Jefferson Pierce/Black Lightning and Jefferson Pierce/Black Lightning
 * Marv Wolfman as Marv Wolfman
 * Robert Wuhl as Earth-89 citizen
 * Nick Zano as Dr. Nate Heywood

Trivia

 * The title of this crossover, Crisis on Infinite Earths, is also the title of a limited series published by DC Comics from 1985 to 1986.
 * Following and, The CW aired a set of TV specials to promote the crossover and reveal behind the scenes details titled.
 * This was the first crossover:
 * Where the title of the crossover was revealed at the end of the previous crossover (​​​​​).
 * To consist of five episodes.
 * To have a one-month break between some of the episodes.
 * The break was accounted for within the crossover.
 * To have major tie-ins with episodes of and  that aired before the crossover.
 * To have a tie-in comic book series. The series is titled . It was two issues long and both issues contained "an in-canon story that ties directly into the crossover narrative" and "characters and concepts that couldn’t be included in the crossover."
 * To have an aftershow. The aftershow was titled.
 * Brandon Routh reprised his role as Superman, having previously portrayed the character in the 2006 film Superman Returns. The iteration of Superman that Routh portrayed is the same character but is now based on the Kingdom Come storyline.
 * All currently airing Arrowverse television series will deal with the fallout from this crossover in the remainder of their current seasons.
 * Both Michael Rosenbaum and Alan Ritchson were offered the chance to reprise their roles as Lex Luthor and Aquaman respectively from the television series Smallville in this crossover. However, Rosenbaum declined and Ritchson had to decline due to scheduling issues.
 * Similarly, Cameron Cuffe was offered the chance to reprise his role as Seg-El from the television series Krypton. However, like Ritchson, he had to decline due to scheduling issues.
 * Nicolas Cage was also reached out to, presumably to portray a version of Superman, a role he was set to portray in the canceled film Superman Lives.
 * Ritchson did ultimately appear in the crossover, albeit in an uncredited cameo as Hank Hall from the television series Titans.
 * When regarding Thawne's absence, “I guess what it really comes down to is not being beholden to a headline from six years ago that was not written by any of the showrunners involved in the crossover,” says Arrowverse EP Marc Guggenheim. “A lot of things drive our stories, and a lot of things determine what choices we make….. To me, tracking toward a headline written six years ago is literally the definition of ‘the cart driving the horse.’ “We’ve had Reverse-Flash so prominent in the Arrowverse over the years, including in last year’s crossover and the crossover before that…. I love the character and I love Tom [Cavanagh] as a person, and I certainly love Matt Letscher’s version, but you have to make choices.”
 * This crossover marked the final appearances of most of all main characters across all Arrowverse shows and introduced new versions of them.