Crisis on Earth - X - wikipedia Crisis on Earth - X `` Crisis on Earth - X '' Arrowverse crossover event Promotional poster Episode nos. Supergirl ( part 1 ) Season 3, Episode 8 Arrow ( part 2 ) Season 6, Episode 8 The Flash ( part 3 ) Season 4, Episode 8 Legends of Tomorrow ( part 4 ) Season 3, Episode 8 Directed by Larry Teng ( Supergirl ) James Bamford ( Arrow ) Dermott Downs ( Flash ) Gregory Smith ( LoT ) Story by Andrew Kreisberg Marc Guggenheim Teleplay by Robert Rovner ( Supergirl ) Jessica Queller ( Supergirl ) Wendy Mericle ( Arrow ) Ben Sokolowski ( Arrow ) Todd Helbing ( Flash ) Phil Klemmer ( LoT ) Keto Shimizu ( LoT ) Original air dates November 27, 2017 ( 2017 - 11 - 27 ) ( 1 & 2 ) November 28, 2017 ( 2017 - 11 - 28 ) ( 3 & 4 ) Episode chronology Supergirl ← Previous `` Wake Up '' Next → `` Reign '' List of Supergirl episodes Arrow ← Previous `` Thanksgiving '' Next → `` Irreconcilable Differences '' List of Arrow episodes The Flash ← Previous `` Therefore I Am '' Next → `` Do n't Run '' List of The Flash episodes Legends of Tomorrow ← Previous `` Welcome to the Jungle '' Next → `` Beebo the God of War '' List of Legends of Tomorrow episodes Preceded by `` Invasion ! '' `` Crisis on Earth - X '' is the fourth annual Arrowverse crossover event, featuring episodes of the live - action television series Supergirl, Arrow, The Flash, and Legends of Tomorrow on The CW. The crossover began on November 27, 2017, with Supergirl and Arrow, and concluded on November 28, with The Flash and Legends of Tomorrow. In `` Crisis on Earth - X '', Barry Allen and Iris West 's friends come to Central City for their wedding, only for the proceedings to be interrupted by interlopers from analogous universe of Earth - X where World War II was won by the Axis Powers. Development for a crossover of the four series began in December 2016 after the release of the previous crossover, `` Invasion ! ''. The premise and title of the crossover were revealed in September 2017 as production on the episodes began ; elements from the animated web series Freedom Fighters : The Ray were part of the crossover, including the live - action appearance of Ray Terrill ( The Ray ), the Freedom Fighters, and the New Reichsmen. Contents 1 Plot 2 Cast and characters 2.1 Main and recurring 2.2 Guest 2.2. 1 Supergirl 2.2. 2 Arrow 2.2. 3 The Flash 2.2. 4 Legends of Tomorrow 3 Production 3.1 Development 3.2 Writing 3.3 Filming 3.4 Music 4 Release 4.1 Broadcast 4.2 Marketing 5 Reception 5.1 Ratings 5.2 Critical response 5.2. 1 Supergirl 5.2. 2 Arrow 5.2. 3 The Flash 5.2. 4 Legends of Tomorrow 6 Notes 7 References 8 External links Plot In the parallel world of Earth - X, a Nazi regime rules the planet, where an archer known as Dark Arrow is the Führer. Dark Arrow seizes a temporal gateway from the Freedom Fighters, which enables interdimensional travel to other universes. On Earth - 1, Barry Allen and Iris West 's friends, including Kara Danvers and her adoptive sister Alex from Earth - 38, come to Central City for Allen and West 's wedding. Harrison `` Harry '' Wells, Cisco Ramon, and Caitlin Snow develop a serum to separate the Firestorm matrix from Martin Stein and Jefferson Jackson. However, Jefferson is reluctant to give up being Firestorm. Oliver Queen re-proposes to Felicity Smoak, but she is hesitant about marrying him. The wedding ceremony is interrupted by invaders from Earth - X led by Dark Arrow, his Kryptonian wife Overgirl, and Prometheus. After Kara injures Overgirl, and Alex and Sara Lance capture Prometheus during the fight, the Nazis retreat. Dark Arrow, who is Oliver 's doppelgänger, and Overgirl, who is Kara 's doppelgänger, unmask themselves as they discuss their next step with the speedster Eobard Thawne, Barry 's nemesis who was previously presumed dead. In S.T.A.R. Labs, Prometheus reveals himself as Tommy Merlyn 's Earth - X doppelgänger, then commits suicide by cyanide pill out of loyalty to the Nazi regime after taunting Oliver. Harry reveals that through his exploration of the multiverse, he discovered that Earth - X is a dystopian world where World War II was not won by the Allied Forces. Dark Arrow, Overgirl, and Thawne steal an experimental sub-light generator, the Prism, from a research company. Oliver 's team, along with Harry, Caitlin, Cisco, and Mick Rory, are in captivity at S.T.A.R. Labs after the Nazi forces occupy it. Oliver, Barry, Sara, Martin, Jefferson, and Alex are abducted to a concentration camp on Earth - X, while Kara is moved to S.T.A.R. Labs. Overgirl is dying from disproportionate insolation in her heart and Dark Arrow plans to use the Prism, powered by S.T.A.R. Labs ' particle accelerator, to create artificial red sunlight that can weaken both Karas ' invulnerability, allowing Thawne to conduct a heart transplant from Kara to Overgirl. In the concentration camp, the heroes are rescued from execution at the hands of SS - Sturmbannführer Quentin Lance ( Quentin Lance 's Earth - X doppelgänger ) by Ray Terrill and Leo Snart ( Leonard Snart 's Earth - X doppelgänger ). Thawne prepares to operate on both Overgirl and Kara, and Iris and Felicity work to rescue their friends at S.T.A.R. Labs. General Winn Schott ( Winn Schott 's Earth - X doppelgänger ), the commander of the Freedom Fighters, is determined to strand Dark Arrow and Overgirl on Earth - 1 by destroying their temporal gateway. While posing as Dark Arrow, Oliver discovers the Nazis ' doomsday device, a timeship called Wellenreiter, a militarized equivalent of the Legends ' Waverider. Oliver allows the timeship to enter Earth - 1 to avoid jeopardizing his cover, but he is ultimately exposed when he refuses to kill Felicity 's Earth - X doppelgänger, a concentration camp prisoner. The heroes struggle against both the Freedom Fighters ' Red Tornado, deployed by Schott as a failsafe, and the Nazi forces, and the gateway 's portal is opened at the cost of Martin being mortally wounded. The heroes make it back to Earth - 1, and Iris, Felicity, Kara, and the others are rescued by the returned heroes and the Waverider crew. Jefferson is also affected by Martin 's injury, so Martin uses the serum to separate the Firestorm matrix and dies from his wounds. His death spurs Oliver to declare war on Earth - X 's Nazi forces. Jefferson tells Martin 's family of his fate ; they, along with the Legends and Barry 's team are devastated by Martin 's death. When the Nazis attack Central City, the heroes counter their assault. Harry, who pilots the Waverider, destroys the Wellenreiter after the heroes disable its shield. Barry spares Thawne, who vows to return. During the fight with Kara, Overgirl 's solar radiation goes nuclear and Kara carries her into space, where Overgirl explodes. Oliver kills Dark Arrow while the latter is in shock over his wife 's death. After Martin 's funeral, Kara and Alex return to Earth - 38, Ray returns to Earth - X after he establishes contact with Earth - 1, and Leo decides to remain on Earth - 1 with the Legends. John Diggle, an ordained minister, officiates Barry and Oliver 's weddings with Iris and Felicity, respectively. Cast and characters Further information : Supergirl, Arrow, The Flash, and Legends of Tomorrow cast and characters Main and recurring Actor Character Episode Supergirl Arrow The Flash Legends of Tomorrow Melissa Benoist Kara Zor - El / Kara Danvers / Supergirl Main Guest Kara Zor - El / Overgirl ( Earth - X ) Mehcad Brooks Guardian ( Earth - X ) Main Does not appear Chyler Leigh Alex Danvers Main Guest Jeremy Jordan Winn Schott Main Does not appear Guest Does not appear Winn Schott ( Earth - X ) Chris Wood Mon - El Main Does not appear David Harewood J'onn J'onzz / Martian Manhunter Main Does not appear Stephen Amell Oliver Queen / Green Arrow Guest Main Guest Oliver Queen / Dark Arrow ( Earth - X ) Victor Garber Martin Stein / Firestorm Guest Main Emily Bett Rickards Felicity Smoak / Overwatch Guest Main Guest Felicity Smoak ( Earth - X ) Caity Lotz Sara Lance / White Canary Guest Main Tom Cavanagh Harrison `` Harry '' Wells Guest Main Guest Eobard Thawne / Reverse - Flash Dominic Purcell Mick Rory / Heat Wave Guest Does not appear Main Candice Patton Iris West Guest Main Guest Franz Drameh Jefferson Jackson / Firestorm Guest Main Danielle Panabaker Caitlin Snow / Killer Frost Guest Main Guest Carlos Valdes Cisco Ramon / Vibe Guest Does not appear Main Guest Grant Gustin Barry Allen / Flash Guest Main Guest Christina Brucato Lily Stein Guest Does not appear Guest Isabella Hofmann Clarissa Stein Guest Does not appear Guest Echo Kellum Curtis Holt / Mister Terrific Does not appear Main Does not appear Guest Rick Gonzalez Rene Ramirez / Wild Dog Does not appear Main Does not appear Guest Juliana Harkavy Dinah Drake / Black Canary Does not appear Main Guest Frederick Schmidt Metallo ( Earth - X ) Does not appear ( non-speaking appearance ) Co-star ( non-speaking appearance ) Wentworth Miller Leonard `` Leo '' Snart / Citizen Cold ( Earth - X ) Does not appear Guest Russell Tovey Ray Terrill / The Ray Does not appear Guest Special Effect Red Tornado ( Earth - X ) Does not appear Guest Brandon Routh Ray Palmer / Atom Does not appear Main Maisie Richardson - Sellers Amaya Jiwe / Vixen Does not appear Main Amy Louise Pemberton Gideon Does not appear Main Tala Ashe Zari Tomaz Does not appear Main Nick Zano Nate Heywood / Steel Does not appear Main ^ Note : Despite being credited, Katie McGrath and Odette Annable do not appear in the Supergirl episode ; David Ramsey, Willa Holland, Katie Cassidy and Paul Blackthorne do not appear in the Arrow episode ; and Jesse L. Martin does not appear in The Flash episode. Guest Supergirl Jesse L. Martin as Joe West Keiynan Lonsdale as Wally West / Kid Flash Jessica Parker Kennedy as a caterer Danielle Nicolet as Cecile Horton Patrick Sabongui as David Singh William Katt as a minister Arrow Colin Donnell as Tommy Merlyn / Prometheus ( Earth - X ) The Flash Paul Blackthorne as SS Sturmbannführer Quentin Lance ( Earth - X ) Legends of Tomorrow David Ramsey as John Diggle Susanna Thompson voices the timeship Wellenreiter 's A.I. Production Development Yearly crossover events in the Arrowverse have occurred on The CW since the 2013 -- 14 television season, when Barry Allen was introduced in the eighth episode of Arrow 's second season ahead of the debut of The Flash. The next year, the eighth episodes of the third season of Arrow and the first season of The Flash formed a two - part event known as `` Flash vs. Arrow ''. In January 2015, The CW president Mark Pedowitz said that there would be an Arrowverse crossover every season. In the 2015 -- 16 television season, a two - part event between the eighth episodes of the fourth season of Arrow and the second season of The Flash was used to set up a new team - up series, Legends of Tomorrow. For the 2016 -- 17 television season, the `` Invasion ! '' crossover included The Flash, Arrow, and Legends of Tomorrow, with the event beginning at the end of Supergirl. Planning for the crossover began in December 2016, with Arrow showrunner Wendy Mericle saying, `` We actually sort of do, believe it or not, have a concept for what we want to do for next year 's crossover. It 's crazy. '' By February 2017, planning began for a true four - way series crossover. Because each series was renewed for an additional season, the producers could plan production schedules to incorporate the crossover. Executive producer Andrew Kreisberg said, `` One of the big things we learned from ( '' Heroes Join Forces `` ), which made ( '' Invasion ! `` ) slightly easier, was building in shut - down days, where shows just went dark. The single hardest factor in doing the crossovers is actors ' availability because the shows keep going on. You 're basically juggling four shows ' worth of schedules. '' That May, Pedowitz confirmed that there were no plans to incorporate Black Lightning in the crossover, as it was not part of the Arrowverse at that time and was scheduled to debut in the middle of the 2017 -- 18 television season. In September 2017, it was revealed that the title of the crossover would be `` Crisis on Earth - X '' and that Ray Terrill ( The Ray ) would make his live - action debut in the Arrowverse, ahead of appearing in the animated web series, Freedom Fighters : The Ray, along with other characters and concepts from that series. Russell Tovey also voices the character in Freedom Fighters. Writing In June 2017, executive producer Marc Guggenheim noted that it would be hard to top `` Invasion ! '' 's threat of aliens, so this crossover would aim to `` increase the emotional stakes and the emotional payoffs ''. The following month, Mericle added that the crossover would be `` very much rooted in the DCU. '' At the Television Critics Association press tour in August 2017, Pedowitz said that the crossover would involve romance, with Berlanti adding, `` our way of making the show bigger this year was to go even more personal, so it 's a big life event for a few different people on the show. There are many life events that happen. '' In September 2017, in a statement revealing the crossover 's title, Guggenheim and Kreisberg said that the crossover was conceived `` to be evocative of the annual Justice League / Justice Society ( comic book series ) crossovers we grew up with and looked forward to as kids. '' The story of the crossover was conceived by Kreisberg and Guggenheim. The teleplay for Supergirl 's episode was written by showrunners Robert Rovner and Jessica Queller, Arrow 's by Mericle and Ben Sokolowski, The Flash 's by showrunner Todd Helbing, and Legends of Tomorrow 's by showrunner Phil Klemmer and Keto Shimizu. Filming Filming of the four episodes began on September 22, 2017. Supergirl 's episode was directed by Larry Teng, Arrow 's by James Bamford, The Flash 's by Dermott Downs, and Legend of Tomorrow 's by Gregory Smith. Music Blake Neely, primary composer of all four series, composed the two - and - a-half - hour score for the crossover in eight days at The Bridge Recording Studio in Glendale, California. La - La Land Records released the soundtrack physically on June 5, 2018, in a limited run. WaterTower Music also released it digitally on June 15, 2018. Professor Murder 's `` Free Stress Test '', Misun 's `` Justice '', St. Lucia 's `` All Eyes On You '', Tom Hillock & Nicolas Boscovic 's `` By the Stream '', Neil Finn 's `` Love Is Emotional '', Kodály Quartet 's `` String Quartet No. 62 in C Major, Op. 76, No. 3, Hob. III : 77, `` Emperor '' : II. Poco Adagio, Cantabile ``, and `` Runnin ' Home to You '' from the musical crossover `` Duet '' performed by Melissa Benoist are heard in the first part of the crossover but not included in the soundtrack. All music composed by Blake Neely, Nathaniel Blume, Daniel James Chan, and Sherri Chung. show Crisis On Earth - X ( Original Television Soundtrack ) No. Title Length 1. `` The Flag Still Stands '' 3 : 20 2. `` We 're Going To The Wedding '' 1 : 19 3. `` Dark Arrow, The Fuhrer '' 1 : 19 4. `` Pretending Nothing Happened '' 1 : 39 5. `` Best Wedding Ever ! '' 4 : 41 6. `` Prometheus - X Locked Away '' 3 : 38 7. `` A Special Kind Of Idiot '' 3 : 14 8. `` Oliver Wants a Yes '' 2 : 26 9. `` Being True To Yourself '' 2 : 32 10. `` Sides Meet - Saving The Building '' 3 : 43 11. `` Big Messy Brawl With Nazis '' 2 : 27 12. `` Dark Arrow Storms The Lab '' 2 : 58 13. `` Overgirl Needs a Heart '' 3 : 18 14. `` March To Their Deaths - Meeting the Ray '' 2 : 34 15. `` Two Warriors '' 2 : 42 16. `` Sneaking Oliver In '' 2 : 03 17. `` Inside Nazi Command Center '' 4 : 25 18. `` Storm Chasers '' 2 : 36 19. `` A Hero Falls '' 1 : 18 20. `` Ending a Tornado To Open a Breach '' 2 : 22 21. `` Breached Back Into Mayhem '' 2 : 56 22. `` Like a Father '' 3 : 52 23. `` Rememberances '' 2 : 31 24. `` Heroes Unite '' 4 : 31 25. `` Disabling The Shields '' 2 : 41 26. `` For The Win ! '' 1 : 49 27. `` A Kiss Goodbye - Surprise Double Wedding '' 4 : 51 Total length : 78 : 18 Release Broadcast Promotional teaser poster. Art by Phil Jimenez The crossover began with Supergirl and Arrow on November 27, 2017, and concluded on The Flash and Legends of Tomorrow on November 28, all on The CW. Arrow, which normally aired on Thursdays at 9 pm, moved to Monday at 9 pm for the crossover and did not air an additional episode on November 30. Pedowitz stated that they decided to have the crossover occur over two nights, as opposed to the four nights of `` Invasion ! '', because The Flash and Legends of Tomorrow were already paired together on The CW 's schedule, and `` it would be better and tighter in terms of storytelling to make it like a two - night, four - hour miniseries. We thought this was a tight, concise way of doing it. '' Guggenheim added, `` We 're really approaching this big four - part event as two back - to - back two - hour movies, and I think when you look at it through that lens, it becomes less important for the Supergirl episode to feel like a Supergirl episode and the Arrow episode to feel like an Arrow episode, which was always our approach in the past. '' Marketing Comic artist Phil Jimenez created a custom cover for the event, which invokes the cover design of the Justice League comic issue # 207, the 20th Annual Justice League of America / Justice Society of America crossover. Promotional trailers for the event were released throughout November, before the full trailer was released on November 20. Reception Ratings Series Air date Rating / share ( 18 -- 49 ) Viewers ( millions ) DVR ( 18 -- 49 ) DVR viewers ( millions ) Total ( 18 -- 49 ) Total viewers ( millions ) Supergirl November 27, 2017 0.9 / 3 2.71 0.7 1.72 1.6 4.43 Arrow November 27, 2017 0.9 / 3 2.52 0.8 1.89 1.7 4.41 The Flash November 28, 2017 1.0 / 4 2.82 0.7 1.83 1.7 4.64 Legends of Tomorrow November 28, 2017 0.9 / 4 2.80 0.8 1.82 1.7 4.62 Critical response Speaking about the crossover as a whole, Jesse Schedeen of IGN felt that `` ultimately, ' Crisis on Earth - X ' set a higher standard for what these crossovers can achieve than last year 's ' Invasion ! ' ''. Scott Mendelson of Forbes said the `` Crisis on Earth - X '' was `` a better Justice League movie than the actual Justice League movie and in many ways was better or at least equal to the best MCU crossover events. '' Rob Leane of Den of Geek thought the crossover was the `` best crossover yet '', saying, `` It offers fresh ideas alongside heaps of fan service, and the special effects wizards behind the scenes make the limited TV budget feel like that of a massive movie. '' Supergirl Schedeen gave the Supergirl episode an 8.1 out of 10. While he felt that the Supergirl episode `` clearly is n't in much of a hurry to get where it 's going '', Schedeen said it did `` prove to be a very entertaining start to the crossover. '' Ultimately, the episode `` did, however, make the most of this massive pairing of heroes, delivering an endless stream of banter and character drama before transitioning into an epic battle royale. There are certainly worse ways to kick off a crossover. '' Caroline Siede at The A.V. Club awarded the episode a `` B + '' rating. She said the episode `` is n't a particularly great episode of Supergirl, but then again it is n't really trying to be. And as the first hour of an ambitious four - part Arrowverse movie, it 's hard to ask for anything more. '' Kayti Burt of Collider gave the episode 4 out of 5 stars, stating, `` I was wildly impressed with the storytelling ambitious ' Crisis on Earth - X ' has shown so far. There were some narrative missteps, but this is like nothing we have ever seen on - screen before : a true comic book - style crossover event that ties hours of superhero serials together in one epic story. '' Arrow Schedeen gave the Arrow episode a 7 out of 10, saying that the episode `` struggled to find that balance between character drama and plot progression, as well as in establishing stakes big enough to support such a massive crossover in the first place. But for all its flaws, at least this episode still included some entertaining moments and a generally strong portrayal of its twisted villains. '' The A.V. Club 's Allison Shoemaker gave the episode a `` B '' rating. She thought it was `` difficult to judge how successful this episode of Arrow is because it 's neither an episode of Arrow nor a complete story, '' but concluded, `` it 's a lot of fun, kind of dumb, and just not as exciting as what came before. Someone has to check those boxes and set up what comes next, and it seems that this time, Arrow drew the ' event ' short straw. '' The Flash Schedeen awarded The Flash 's episode a 9.2 out of 10, noting that while part 1 had `` a slow start '' and part 2 gave `` a fairly underwhelming follow - up... the crossover finally seemed to click '' in part 3. Scott Von Doviak at The A.V. Club gave the episode a `` B + '' rating, stating `` Even a lesser installment like this one features the spectacle of the Flash and The Ray battling the Red Tornado, as well as the appealing non-superpowered Nazi - fighting team of Iris and Felicity. For the most part, I 've felt like a kid coming home with a fresh stack of comics, and I can think of no higher praise than that. '' Mike Cecchini of Den of Geek gave it 4 out of 5 stars. He wrote that while `` ' mirror universe Nazis ' do n't make for the most nuanced of villains, and when you 're using concentration camp imagery, well, you 'd better make sure you 're not being exploitative, '' The Flash 's episode `` completely embraces its lunacy in ways that I do n't even think those first two chapters dreamed of. '' Legends of Tomorrow Schedeen gave the final episode an 8.5 out of 10 rating. The episode `` did n't have quite the urgency it needed during the final showdown between good and evil, '' but `` did make the most of Professor Stein 's heroic sacrifice and its emotional fallout. '' Oliver Sava of The A.V. Club gave the episode an `` A '' rating, stating `` No piece of live - action superhero media has captured the feeling of a comic - book crossover event like Crisis On Earth - X. With a huge cast of characters, a major death, and a final scene taking big heroes in bold new directions, Crisis delivers the thrills, the twists, and the inspiration that should come from a superhero story with this massive scope. '' Jim Dandy from Den of Geek rated the episode 5 out of 5 stars. He wrote, `` This year 's was an objectively wonderful hour of DC television, but it also moved the season 's story along for Legends in a meaningful way, and provided significant character development for Jax and Sara. It gave Franz Drameh and Victor Garber a chance to stretch their acting wings, and it closed out a timely, wall - to - wall entertaining four hours of television. '' Collider 's Carla Day gave the Legends episode 5 stars out of 5, saying the crossover was `` leaps and bounds better than any of the previous crossovers. '' She went on to say that `` It set the standard high for all future crossovers in the story, character interactions, and fight scenes. '' Notes Jump up ^ The final episode of the fourth season of The Flash revealed Kennedy 's character to be Nora West - Allen, the daughter of Barry and Iris. References ^ Jump up to : Burlingame, Russ ( November 9, 2017 ). `` ' Crisis on Earth - X ' Arrowverse Crossover Description Released ''. Comicbook.com. Archived from the original on November 10, 2017. Retrieved November 10, 2017. ^ Jump up to : Wickline, Dan ( November 18, 2017 ). `` CW Releases 92 Images From Arrowverse Crossover : Crisis On Earth - X ''. Bleeding Cool. Archived from the original on November 18, 2017. 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Jump up ^ Burlingame, Russ ( May 16, 2018 ). `` Arrowverse `` Crisis on Earth - X '' Crossover Soundtrack Getting Official CD Release ``. Comicbook.com. Archived from the original on May 20, 2018. Retrieved May 20, 2018. Jump up ^ iTunes https://itunes.apple.com/us/album/crisis-on-earth-x-original-television-score/1397579889. Retrieved 24 June 2018. Missing or empty title = ( help ) Jump up ^ Amazon https://www.amazon.com/s/ref=nb_sb_ss_c_1_10?url=search-alias%3Ddigital-music&field-keywords=crisis+on+earth+x&sprefix=Crisis+on+%2Caps%2C208&crid=256O95Y9SW68M. Retrieved 24 June 2018. Missing or empty title = ( help ) Jump up ^ Abrams, Natalie ( August 2, 2017 ). `` CW sets two - night event for four - way superhero crossover ''. Entertainment Weekly. Archived from the original on August 4, 2017. Retrieved August 4, 2017. Jump up ^ Abrams, Natalie ( November 6, 2017 ). `` CW releases first look at Crisis on Earth - X superhero crossover ''. Entertainment Weekly. 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Retrieved November 29, 2017. ^ Jump up to : Porter, Rick ( December 15, 2017 ). `` CW crossovers get another bump in week 10 broadcast Live + 7 ratings ''. TV by the Numbers. Archived from the original on December 15, 2017. Retrieved December 15, 2017. ^ Jump up to : Porter, Rick ( November 30, 2017 ). `` ' The Flash, ' ' This Is Us ' and ' Rudolph ' adjust up : Tuesday final ratings ''. TV by the Numbers. Archived from the original on November 30, 2017. Retrieved November 30, 2017. Jump up ^ Schedeen, Jesse ( December 1, 2017 ). `` Arrowverse : Why the ' Crisis on Earth - X ' Crossover Topped ' Invasion ! ' ''. IGN. Retrieved December 7, 2017. Jump up ^ Mendelson, Scott ( November 29, 2017 ). `` The Year 's Best ' Justice League ' Movie Did n't Need Batman Or Superman ''. Forbes. Retrieved December 7, 2017. Jump up ^ Leane, Rob ( December 7, 2017 ). `` DC TV : why the Crisis On Earth - X crossover was the best yet ''. Den of Geek. Retrieved December 7, 2017. Jump up ^ Schedeen, Jesse ( November 27, 2017 ). `` Supergirl : ' Crisis on Earth X, Part 1 ' Review ''. IGN. Retrieved December 7, 2017. Jump up ^ Siede, Caroline ( November 27, 2017 ). `` Supergirl hops Earths, punches Nazis as The CW 's crossover extravaganza begins ''. The A.V. Club. Retrieved December 7, 2017. Jump up ^ Burt, Kayti ( November 27, 2017 ). `` ' Arrow ' and ' Supergirl ' Recap : ' Crisis on Earth - X ' Parts 1 & 2 ''. Collider. Retrieved December 7, 2017. Jump up ^ Schedeen, Jesse ( November 27, 2017 ). `` Arrow : ' Crisis on Earth - X, Part 2 ' Review ''. IGN. Retrieved December 7, 2017. Jump up ^ Shoemaker, Allison ( November 28, 2017 ). `` The crisis continues in Arrow 's piece of The CW 's Earth - X crossover ''. The A.V. Club. Retrieved December 7, 2017. Jump up ^ Schedeen, Jesse ( November 28, 2017 ). `` The Flash : ' Crisis on Earth - X, Part 3 ' Review ''. IGN. Retrieved December 7, 2017. Jump up ^ Von Doviak, Scott ( November 28, 2017 ). `` The Flash gets lost in an overstuffed chapter of an entertaining crossover event ''. The A.V. Club. Retrieved December 7, 2017. Jump up ^ Cecchini, Mike ( November 29, 2017 ). `` The Flash Season 4 Episode 8 Review : Crisis on Earth X Part 3 ''. Den of Geek. Retrieved December 7, 2017. Jump up ^ Schedeen, Jesse ( November 28, 2017 ). `` DC 's Legends of Tomorrow : ' Crisis on Earth - X, Part 4 ' Review ''. IGN. Retrieved December 7, 2017. Jump up ^ Sava, Oliver ( November 28, 2017 ). `` Crisis On Earth - X ends with big twists and a massive superhero showdown ''. The A.V. Club. Retrieved December 7, 2017. Jump up ^ Dandy, Jim ( November 29, 2017 ). `` Legends of Tomorrow Season 3 Episode 8 Review : Crisis on Earth - X Part 4 ''. Den of Geek. Retrieved December 7, 2017. Jump up ^ Day, Carla ( November 28, 2017 ). `` ' The Flash ' and ' Legends of Tomorrow ' Recap : ' Crisis on Earth - X ' Parts 3 & 4 ''. Collider. 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Question: what episode of the flash is crisis on earth x
Answer: Season 4, Episode 8