This episode is the fourth of the four-part Crisis on Earth-X Crossover event between Supergirl (2015), The Flash (2014), Arrow, and Legends of Tomorrow. The episodes in chronological order are "Crisis on Earth-X, Part 1", "Crisis on Earth-X, Part 2", "Crisis on Earth-X, Part 3", and "Crisis on Earth-X, Part 4".
The rest of the Legends return to Earth-1's present time, just as the heroes trapped in Earth-X have also made their way back. Now that all the heroes of Earth-1 are together once more, they have to pool all their efforts into finally ridding their world of the Earth-X Nazis.
Tropes:
- Action Film, Quiet Drama Scene: After the epic escape from STAR Labs, the heroes finally rendezvous to get on to the Waverider. And then they spend a bit of time in the ship coping with Stein's Heroic Sacrifice.
- Altar the Speed: Barry and Iris decide to go for a quick marriage since they've already done the ceremony, grabbing Diggle since he's an ordained minister, and Felicity decides to marry Oliver on the spot since they have him there.
- Badass Army: After the other Legends finally return (and even bust the heroes out of the Pipeline) and the main party returns from Earth-X with a couple of new allies in tow, the Earth-X invaders find themselves facing off against a small army of very pissed supers.
- Barehanded Blade Block: Ray catches Thawne's scalpel while microscopic, leaving Thawne befuddled until Ray returns to normal size and blasts him.
- Big Damn Heroes: The rest of the Legends sweep in to save Felicity, Kara and Iris. Special mention goes to a shrunken Ray doing a Barehanded Blade Block to the scalpel Thawne tries to cut up Kara with.Ray/The Atom: Mitts off, Mengele!
- Big "NO!": Dark Arrow's response to Overgirl's death, complete with momentarily falling to his knees in despair.
- Bittersweet Ending: The invasion is repelled, Dark Arrow and Overgirl are dead and both Barry and Iris as well as Oliver and Felicity get married. However, Earth-X still isn't freed from Nazi control and the Reverse-Flash pulls a Karma Houdini yet again. Plus, Stein is dead.
- Brick Joke: When all is said and done, it seems this is the very first annual event that doesn't feature John Diggle...until the very end, where Barry kidnaps him because Felicity tells Barry he's an ordained minister.
- Brought Down to Normal: After Stein's death, Jax naturally can't transform into Firestorm any longer. Thus, he doesn't participate in the final battle. Instead, he gives Clarissa and Lily his condolences.
- But Now I Must Go: Once the crisis is resolved, (The) Ray returns to Earth-X to continue their fight. Leo on the other hand decides to stick around on Earth-1 for a while.
- Call-Back:
- When Mick encounters Citizen Cold after drinking a few beers, he literally knocks himself on the head, and laments that he's seeing hallucinations again.
- When Supergirl falls back to Earth, Nate catches her and quips, "I thought it would take a man of steel to save the Girl of Steel," harkens back to when Rip mentions seeing "men of steel die."
- Calling Your Attacks: At the helm of the Waverider, Cisco announces firing a torpedo, with Wells telling him that he doesn't have to say it aloud.
- Casting Gag:
- Susanna Thompson, who played Moira Queen, voices the Earth-X version of Gideon on Der Wellenreiter.
- It's also not the first time she's played a malevolent cyberintelligence.
- Catch a Falling Star: Nate caught Supergirl after she's falling from the lower atmosphere.
- Character Death: Aside from the deaths of Overgirl and Dark Arrow, Martin Stein also dies.
- Combination Attack:
- Ray combines his light blasts with Flash's lightning throw to finally stop Red Tornado.
- Metallo gets defeated by every hero present combining their powers, hitting him from all sides and obliterating him. This is also a possible Continuity Nod to how the Legends defeated the Pilgrim in Season 1.
- Curb-Stomp Battle: Metallo is on the receiving end of one from the combined firepower of the Legends, Team Flash and Arrow, and the Ray.
- Defeat Equals Explosion: Overgirl blew up in the lower atmosphere.
- Determinator: Even after being shot multiple times, Stein still finds the energy to drag himself to the switch and activate it.
- Do Not Go Gentle: Critical from getting shot, Martin Stein didn't just lie down and stay there, he instead musters up the strength to get to the console and activate the teleporter, vaporizing some of the Nazis in the process.
- Dope Slap: After Sara and Alex share a parting hug and say goodbye to each other, Mick asks Sara "You hit that?" To which she responds by dope-slaping him. "Shut up."
- Evil Counterpart: There is even a red, evil version of Gideon inside the Wellenreiter.
- Failed a Spot Check: Was Ray so small that Thawne couldn't see him literally under his nose (and scalpel)?
- Fastball Special: In the final fight, Mister Terrific throws a T-sphere with a shrunken Ray riding aboard.
- Heroic Sacrifice: Stein elects to detach from Jax as Firestorm to save the latter from his fatal injuries.
- Hidden Depths: Felicity's grandparents were Holocaust survivors.
- Hope Spot: At first it seems like Stein could be fine, due to merging with Jax again, only for both lives being threatened by this and Stein having to pull a Heroic Sacrifice.
- Hostage Situation: Dark Arrow has Felicity at bow-point while Arrow has a scalpel to depowered Overgirl's neck. Each hostage refuses to act as such before Thawne whisks away his allies.
- I Choose to Stay: Leo makes the decision to stay on Earth-1 for a while.
- Idiot Ball: Barry just letting Thawne run away. It's not like he couldn't have locked him up instead of having to choose between killing him and letting him run free. Somewhat justified, as Thawne would just find a way to return anyway due to the Timey-Wimey nature of his existence.
- Internal Reveal: Ray learns that Thawne is alive again. He even lampshades how that jerk is supposed to be dead.
- Irony:
- Turns out Rory-X died running back into a burning police station to save cops. Rory feels so sick he actually stops drinking.
- Dark Arrow mocked the heroes for their empathy, claiming Love Is a Weakness. His love for Overgirl gets him killed when her death distracts him long enough for Green Arrow to have him dead to rights when he decides to start fighting again.
- The last time Eobard Thawne worked on a villainous team, he was the only member of the team to actually die. This time around, he's the only member of the villainous team to actually survive.
- It's All My Fault: Jax beats himself up over Stein's death, thinking that he shouldn't have convinced him to stay on the Waverider longer.
- Karma Houdini: Eobard Thawne, yet again, to the point he may just have inherited what was previously Merlyn's Joker Immunity.
- Kick the Dog:
- Overgirl and Dark Arrow lead their troops to a completely needless civilian massacre right in the middle of Central City.
- Thawne alludes to stealing another person's face if and when he and Barry see each other again.
- Killing Your Alternate Self: Oliver kills his Earth-X counterpart to avoid being shot by him.
- Laser-Guided Karma: Oliver-X is killed in the exact same manner as he killed Guardian-X at the beginning of the crossover.
- Mirror Match: Three of them this time — Supergirl vs. Overgirl again, Green Arrow vs. Dark Arrow again, and the Waverider vs. Der Wellenreiter.
- Mook Chivalry: The Nazi troops just walk up to the heroes instead of shooting them with their, y'know, guns. Even though most of them are not super-durable. Seconds later, we see them using grenades on civilians.
- Mythology Gag:
- Leo reminisces about how "his" Mick Rory died saving police from a fire. He's basically calling Rory-X a firefighter in all but name, which is Comic!Heatwave's occupation during his time as a changed man.
- "General, would you care to step outside?" is uttered by Supergirl to Overgirl, a line lifted from Superman II.
- The Flash and Reverse-Flash moving so fast that the entire war around them looked frozen in time, just like the finale of Justice League: The Flashpoint Paradox.
- Harry tells Supergirl that she has to take Overgirl, who is in the middle of a Superpower Meltdown, "Up, up, and away" from her current location.
- The bit about Kara-X overclocking in the atmosphere also happened to Firestorm in Identity Crisis (2004), Captain Marvel in Kingdom Come, and Captain Atom in Injustice: Gods Among Us.
- Nate also refers to himself as a Man of Steel.
- Oh, Crap!: A Nazi saw a wounded Stein is about to turn on the portal he and his comrades are standing on. He tells them to fall back, but it's too late.
- One-Steve Limit: Averted, there are two Rays around in this episode.
- O.O.C. Is Serious Business: When Mick of all people tries to calm Jax down over Stein's injuries, you know it's serious.
- Orbital Shot: The camera rotates around a few of the heroes standing in a circle starting when Oliver asks if they've located the Earth-X Waverider.
- Relocating the Explosion: In the climax, Kara's evil doppelganger Overgirl is about to explode with the force of a nuke from Superpower Meltdown. Supergirl has to fly her "Up, up, and away" so that the explosion happens in the upper atmosphere, sparring the city.
- Retirony: Surprising absolutely no one, Stein gets fatally shot just as he's declared he's days away from retirement and he and Jax have both confessed to their father-son relationship.
- Running Gag: Diggle still gets nauseous when Barry speeds him somewhere.
- Sacrificial Lion: Stein is the major casualty of the crossover.
- Screw Your Ultimatum!: Dark Arrow tries to offer a truce: he'll retreat to Earth-X with Der Wellenreiter if he's allowed to take Kara. Arrow explains how he won't abandon his friends then hangs up on him.
- Shipper on Deck: Diggle has been keeping Oliver and Felicity together for almost six years. He deserves to officiate their wedding!
- Shout-Out:
- Ray squashes a Nazi mook with an oversized hand and refers to it as "embiggens" like Marvel's Kamala Khan.
- Harry Wells quotes lines from Star Wars and Top Gun in his banter with Cisco at the helm of the Waverider. Either Earth-2 has the same movies, or he watched them while on Earth-1.
- Right after they refer to Metallo as The Terminator, his head flies off during destruction like the Cromartie Terminator from Terminator: The Sarah Connor Chronicles.
- Significant Wardrobe Shift: For the climatic battle, Zari ditches her civilian attire for a more proper costume with a black and gold color scheme, a Mythology Gag to the look of Black Adam. She claims she doesn't want to look out of place among the rest of the defenders, who have all donned their superhero duds.
- Skewed Priorities: Dinah scolds Cisco over getting amused by pop culture references (one she made, no less) in the middle of a battle.
- Save the Villain: Played with but averted. Oliver-X is so shocked at his wife's death that Oliver could kill him easily—he has an arrow ready but refuses to shoot his Evil Counterpart In the Back. But then Oliver-X angrily says I'll Kill You! and turns to fire, only to catch an arrow in the heart.
- Stealth Pun: The Atom rides a T-Sphere, shooting a bunch of Nazis before growing back to normal size to uppercut another. So basically, Mr. Terrific literally threw a fastball.
- Strike Me Down with All of Your Hatred!: Thawne goads Barry into this, then mocking him, seeing that he still doesn't have it in him.
- Suicidal Cosmic Temper Tantrum: Overgirl wants to detonate herself in the middle of Central City, killing as many people as possible.
- Superpower Meltdown: Overgirl goes critical and explodes. Thankfully, Supergirl flies her into low orbit so the explosion doesn't harm anyone.
- Taking You with Me: After realizing that she has no more chances of survival, Overgirl decides to at least take as many people with her as possible before exploding right over Central City.
- Team Power Walk: An epic one with most of the heroes coming in to face the Nazi soldiers precedes the final battle.
- That's What I Would Do: Oliver quotes the trope when he predicts exactly what Dark Arrow will do (attack Central City and offer to stop in exchange for Kara) because he'd do the same thing.
- There Is No Kill Like Overkill: Metallo-X receiving a barrage of attacks from a half dozen of the heroes in multiple directions.
- Thou Shall Not Kill: Averted with Oliver, who initially considers sparing his doppelganger (or at least refuses to shoot him In the Back), only to kill him in self-defense when he attacks him out of rage.
- Together in Death:
- Overgirl and Earth-X Oliver died nearly at the same time. After Overgirl dies from her condition, Oliver kills his Earth-X counterpart.
- Stein is dead, as is his former partner Ronnie.
- Too Dumb to Live: The group of Nazi soldiers who proceeds to charge the group of heroes instead of firing their weapons.
- Villain: Exit, Stage Left: After Barry refuses to kill Thawne, he promptly leaves, having no loyalty to Earth-X. He wonders what face he'll be wearing the next time he and Barry meet.
- Villainous Breakdown: Dark Arrow begins having one after it is clear that Overgirl is going to die, no matter what, proceeding to order his troops to destroy Central City. Then, after Overgirl detonates, Dark Arrow first has a Big "NO!" and falls to his knees, then gets up to try to kill Earth-1 Oliver anyway. His breakdown is short-lived, as he immediately gets an arrow to the chest after standing up.
- Villainous Valor: Even after all of his troops have been beaten, Thawne has deserted him and Overgirl is dead, Dark Arrow still tries to attack Green Arrow. It does him no good.
- Weddings for Everyone: The episode ends with a double wedding of Barry and Iris, and Oliver and Felicity.
- What Measure Is a Mook?: Snart actually scolds Mick for roasting Nazis left and right instead of granting them due process. It's not clear if he is serious or just trolling Mick, since this attitude wouldn't have served him well on Earth-X.
