Crisis on Infinite Earths: Part Three

"It is time... to end the age of heroes, and everything you hold close."

- Mobius, speaking through a possessed Harbinger

This episode is also the ninth and final in a subset of the sixth season episodes the writers dubbed as "Blood and Truth."

The episode is the third part of the five-part crossover, ​.

Starring

 * Grant Gustin as Barry Allen/The Flash/Green Arrow
 * Candice Patton as Iris West-Allen
 * Danielle Panabaker as Dr. Caitlin Snow/Frost
 * Carlos Valdes as Cisco Ramon/Vibe
 * Hartley Sawyer as Ralph Dibny/Elongated Man
 * Danielle Nicolet (credit only)
 * LaMonica Garrett as Mar Novu/The Monitor and Mobius/Anti-Monitor (voice)
 * Tom Cavanagh as Dr. Nash Wells/Pariah
 * Jesse L. Martin (credit only)

Special appearance by

 * Jon Cryer as Lex Luthor
 * Matt Ryan as John Constantine
 * Tom Ellis as Lucifer Morningstar

Special guest star

 * Stephen Amell as Oliver Queen/Green Arrow/The Flash
 * Caity Lotz as Sara Lance/White Canary
 * Brandon Routh as Dr. Ray Palmer and Superman
 * David Ramsey as John Diggle
 * Katherine McNamara as Mia Smoak
 * Elizabeth Tulloch as Lois Lane
 * David Harewood as J'onn J'onzz
 * Tyler Hoechlin as Superman
 * Cress Williams as Jefferson Pierce/Black Lightning
 * Ruby Rose as Kate Kane/Batwoman
 * Melissa Benoist as Kara Danvers/Supergirl

Guest starring

 * Ashley Scott as Huntress
 * Audrey Marie Anderson as Harbinger and Mobius/Anti-Monitor
 * Osric Chau as Dr. Ryan Choi
 * Stephen Lobo as Jim Corrigan
 * John Wesley Shipp as Barry Allen/The Flash

Featuring

 * Wentworth Miller as Leonard A.I. (voice)

Uncredited

 * Dina Meyer as Oracle (voice)
 * Rick Gonzalez as Rene Ramirez (archive footage)
 * Juliana Harkavy as Dinah Drake (archive footage)
 * Amanda Pays as Tina McGee (archive footage)

Plot
Earth-203 - New Gotham A pink hue has completely engulfed the sky and all surrounding areas, as far as the eye can see. A tall woman with dark hair dressed in all black with a long black trench coat is running from rooftop to rooftops while trying to speak with someone through her earpiece. She is desperately trying to get a hold of Oracle, who through the static communication insists she is sending all relative information. A brilliant white light begins to consume the city, taking over a tall building that resembles Wayne Enterprises. The dark-haired woman, Huntress is devastated to lose contact with her friend before she too vanishes.

Earth-1 - Waverider Inside the Waverider, seven people remain including both Supermen. Mar Novu reminds them they have only located four of the seven Paragons. Ray is off to the side, insisting what he is doing is a very difficult and time-consuming task. The room lights up with the arrival of the rest of Team Flash. Ray is excited to have Cisco join them, please to have someone he can talk out the math with. Ralph is very surprised to see a doppelgänger of Superman, while Frost tells everyone to ignore him, as he is new, and this is his first crossover. Novu interrupts, reminding everyone that the wave is moving rapidly, and Earth-1 will be the final world to be destroyed. Supergirl informs them that Alex and Brainy are still safe and everyone from Earth-38 is still present and accounted for, regardless of the continuing distractions of all the other universes. They decide to bring as many people as they can to Earth-1, trying to save whoever they can across the multiverse. J'onn tells everyone he can use his psychic abilities to keep everyone connected within the Waverider. Lois decides to return to the legion ship, because parallel Earth Rory still has baby Jonathan, and she will keep everyone updated from her end.

Everyone is interrupted with the excitement from Ray and Cisco, having finished working on finding out who the remaining Paragons are. Batwoman asks what's taking so long and Cisco tells her to wait as the machine is some buffering. It is revealed that The Flash is the "Paragon of Love", "J'onn J'onzz" is the "Paragon of Honor" and Dr. Ryan Choi is the "Paragon of Humanity". Which means the only person they don't have a location on is Dr. Ryan Choi. Luckily he is in Raymond's hometown at Ivy University. Ray, Ralph, and Iris all decide to go collect him. The Monitor confirms now that the final Paragons have been identified, they next must determine how to stop the antimatter wave. They are interrupted with Leonard announcing Diggle's arrival.

Earth-1 - Waverider In the infirmary, Dig is furious to find an unconscious and half dead Oliver. Sara tries to calm him, but Dig insists he should have been there to protect him. Sara reveals they are looking to bring him back, the same way Olly brought her back. Though he doesn't like it, Dig insists he is coming with them. The Monitor arrives and unceremoniously informs Dig that Harbinger is missing. Dig loses his temper and insists he is not losing his wife or his best friend. Both of them team up against The Monitor, and he admits the Harbinger could possibly be with his adversary, the Anti-Monitor.

The Monitor explains to the room, now in front of the rest of the heroes who their real enemy is. He informs them all that he has been preparing them and testing them to learn their limits for a long time now. He needed their courage and honor as well as their strength and everything else the Paragon stands for. Because he needed the greatest heroes, in order to defeat their greatest threat. The Anti-Monitor's goal is to eliminate the multiverse and replace it with his own design. Supergirl isn't surprised, insisting he is like every other megalomaniac. The Monitor admits he should have seen that his connection with the Harbinger could be used against him. Dig doesn't care and just wants to know how to get his wife back, their interests to find her falls on deaf ears. He cannot rewrite history, he can only attempt to save what remains. Supergirl is upset with the conversation and leaves to cool her head. Batwoman watches her go, taking out the Kryptonite Bruce Wayne gave her, and questioning if she will have to use it. Sara promises to watch over Oliver's body while Dig, takes Mia to find Ollie's soul.

Frost and Cisco are both in the control room and Cisco is excited when he announces he is trying to determine where the antimatter Wave-Particle is on Earth, to locate the source of the waves and he has discovered its located at a subterranean region very close to them. Excited, he tells Frost to meet him in the cargo bay. On his way there he is startled to run into The Monitor, having just left him in the control room. Their The Monitor informs him it is time for him to become Vibe again. Against Cisco's protest, he immediately transforms him into Vibe, giving him his powers back.

Flash and Iris are saying their goodbyes to each other, Iris is still worried of the prophecy about losing her husband in the Crisis. Iris asks him if he's sure he still wants her to go to Ivy Town, and Flash insists she must. They share a tender moment before Flash goes with Frost and Cisco.

Earth-1 - Central City Cisco is able to breach the three of them to the underground bunker; Barry immediately speeds off to run a perimeter search. Frost and Cisco make it to the end of the hallway and they are standing before a wall encrypted with a set of symbols. A total of seven hieroglyphics. Both of them are interrupted by the presence of Pariah he re-introduces himself to the group, insisting he is no longer Nash and has only arrived to bear witness to tragedy. Cisco is neither surprised or impressed with his new name and look. When pressed as to what happened to him, Pariah admits he was searching these tunnels for Mar Nova in order to kill him, expose him as a false god, only to be controlled by another god, the Anti-Monitor. He had laid the perfect track for him, manipulating him to gain a foothold into this universe. They ask Pariah if he remembers how to open the door, but he does not. Pariah then reminds Cisco he can now vibe Nash's old memories. It works and Cisco is able to unlock the door behind the hieroglyphics.

Earth-1 - Waverider Supergirl and Batwoman are in the holding cell with Lex Luthor who is entertained with their predicament. Supergirl questions on whether or not it's possible to bring back Earth-38, and he declines to give a clear answer. Batwoman has become annoyed with Lex and takes down the force shield holding the man, and slams him against the wall, demanding answers. Lex again makes a joke, but Batwoman twists his arm harder behind his back. Lex admits in order to use the Book of Destiny you must focus on what you want without hesitation, when question what he focuses on, Supergirl answers that it is his hatred for Superman. Lex confirms she got it on her first try. Lex Luthor surprisingly cautions them, killing someone is easy, but trying to bring back an entire universe or world would drive the person insane. Just like Deegan. Kate puts Lex back in his invisible cell, concoctions Kara against using the book, as they don't know what kind of effect it could have. She questioned since she is the Paragon of Hope maybe she is supposed to do this, in order to bring back Earth and Argo City, upset Kara leaves the room.

Earth-666 - Los Angeles John Constantine, Mia and Dig are all traveling together down the dimly lit alleyway with bright neon lights in the City of Angels. John knocks on a door only to have his old friend Lucifer answer. He has two beautiful women on either side of him, who he graciously sends away in order to conduct business. It is clear the two have a history, and after introducing himself, he hypnotizes Mia and seductively asking her what she wants. She confirms she's only here to find her father. John briefly explains it is of the utmost importance, and that Lucifer owes him. Never one to be in debt, Lucifer hands him a card with the devil on it. He warns they have until the card fades in order to find their friend. Happy to have finished his business, he closes the door on them. Mia is annoyed that he never told them how to get to Purgatory, but John assures them he already knows how. He holds the card out in front of them, while the card lights up, sending them all away.

Purgatory The three of them have found themselves on a replica of the Lian Yu island. Dig is surprised at their arrival, but Mia reminds them that the island's name is Mandarin for purgatory. John cautions them; a man without a soul is not easy to deal with, and will most likely not remember them.

Team Arrow is quickly losing time while looking for Oliver as their card has already begun to fade. They are all extremely surprised when a depressingly dressed Oliver Queen emerges from the forest attacking them, knocking out Dig and putting John in a headlock. Frantic, Diggle begins to try to talk down his long-time friend. Apologizing for not being there to help save him, but that no matter what they are brothers until the end. This seems to connect with the angry man before them, who puts John down and hugs his friend with both arms. He breaks away to hug his daughter as well.

John reminds them it's time to immediately leave. Before they can, the group is interrupted with the presence of another man. His name is Jim Corrigan. He is an older man with dark hair and a slim trim. He informs them that he used to be a decorated police officer, but was eventually called to a higher purpose to become a spectre, he says this while his eyes briefly glow green. Mai is unimpressed and tells him to leave. Jim turns to Oliver, informing him, it is now his turn, to serve a higher purpose. And that his destiny is to save everyone, otherwise all the universes and everyone he loves will perish. Oliver seems to know he can believe and trust this man and agrees. His daughter and friends are sent away, leaving Oliver alone once again.

Nexus Barry returns, confirming there are no quantum towers around. They all enter the hidden room together. Having left the old dingy brick laid halls, they enter a very clean and chic, futuristic-looking room. Cisco says the room has an intense amount of vibrational frequency surging through it. Pariah tells them that this is the nexus between the antimatter universe and their own. In the middle is a bright white light beaming up towards the sky and the energy is surrounded by red lights with a darker red vibrating in the front of it. Which just so happens to be the anti-matter's source of the wave. Frost questions if the blur is alive. Barry uses his speed to run forward, only to be very shocked and surprised to see Barry Allen from Earth-90 continuously running at light speed on a treadmill. The Earth-90 Flash warns him to stop, but Barry doesn't react in time and hits the force field surrounding the older man. Pariah reminds them that the last time they faced off against The Monitor the speedster disappeared in a puff of smoke and had been missing ever since. All part of the greater plan. The anti-Monitor corralled his speed and used it to build his antimatter cannon, which he tested by destroying the first earth, Earth-2. It is only then, that they realize both Harry and Jesse are now gone. It is during this time they realize Pariah is missing.

Flash insists they have to get their old friend off of the treadmill. He convinces Vibe that this is why The Monitor gave him his powers back, so he opens a portal directly in front of The Flash who unwillingly is forced through. Earth-90 Barry thanks them after hitting a wall, but insists he must go back. The canon begins to erupt as it powers down. Earth-90 Barry insists, unless he continues to power it, it will just immediately destroy all the remaining Earths as a countermeasure to keep him running.

Team Flash is incredibly surprised to see a man dressed in black with two gold lightning bolts down his body entered the room. He demands to know where he is and who the people before him are, he then strikes at them with one of his lightning attacks. Before he can do it again, the Flash steps forward and sends his own attack back, but is sent flying against a monitor and crashes it. Pariah re-appears before them again introducing Jefferson Pierce as Black Lightning. Jefferson reluctantly informs them he was brought here to help as his world has been destroyed. Black Lightning cries Pariah should've saved his family instead of him. Earth-1 Barry Allen tells him he understands how he feels, but right now they have to try and save the Earth they are currently on, as it will be the final Earth and all the multiverse will be destroyed. They asked Black Lightning for his help which he agrees to, absorbing the electricity from the machine, giving Team Flash more time.

Realizing they are quickly running out of time, both Barry Allens use their super speed to begin communicating. Earth-1 Barry confesses how worried he is, the more time they waste another world dies, and he can't lose his wife. Earth-90 Barry reveals to him he was married once too. Her name was Tina and her purpose in life was to keep him running, and he's been doing that for the past 30 years. This caused something in Earth-1 Barry to click, finally understanding what The Monitor meant that day in the Time Vault. Realizing that this is what he has been running towards all these years. Insisting it's time for the Flash to vanish in Crisis. Cisco informs them, "reversing the trail mellows directional velocity could make the antimatter wave received and funneled back into the speed canning, destroying the machine, once and for all"

Realizing it must be him, Barry begins to say his goodbye to his friends. Commenting that Caitlin and Cisco were the first people he ever saw after becoming/when he opened his eyes that day in the hospital. Insisting he couldn't have been a hero without them. He adds to tell his wife and Joe how much he loves them and they both promised to do so. He is interrupted by the older Flash apologizes before momentarily stealing his speed. Telling him that when you've been a speedster as long as he has, you pick up some neat tricks. Earth-1 Barry cries out wanting to know why, Earth-90 Barry says The Monitor said The Flash had to die during Crisis, but he never said which Flash. Wanting the younger man to live a longer life. He takes a moment to tell Jefferson how amazing a hero he is too. He then instructs Cisco to open the breach. Cisco is hesitant, but the older man reminds him that this way his friend won't have to die, while Earth-1 Barry pleads for his friend not to do it. Reluctantly, Cisco opens the breach allowing Earth-90 Barry through. Once on the treadmill he begins running at super speed again, Cisco opens another breach for them to escape through, everyone leaves as Cisco forces Barry to come with them. Now that Earth-90 Barry is left alone in the room, he holds onto his final moments of remembering his wife Tina. Before the energy destroys him. He managed to stop Earth-1's immediate destruction, saving everyone. All that is left behind is the lightning bolt symbol from his chest.

Earth-1 - Ivy Town With the antimatter cannon down, the entire skyline of Earth-1 has turned the same daunting red as all the other worlds prior to it. Ray, Iris, and Ralph all find Dr. Ryan Choi alone in his laboratory on the phone to his wife. He immediately gets off the phone when he realizes his hero, Dr. Ray Palmer is standing before him. He is incredibly shocked and surprised, and begins gushing over him, insisting his second paper on subatomic density manipulation was the foundation for his work on miniaturization. Iris interrupts them insisting they need him to come with them immediately. Ray quickly explains they're heroes, and the doctor for obvious reasons does not believe that. Elongated Man takes this time to stretch out his arm across the room and give the man a Kleenex. They insist Ryan is a Paragon and they need him to help save the universe, quite freaked out by everything Ryan backs out of the room, wanting to spend his final moments with his wife and child.

Ryan is frantically packing his things at his office but takes a moment to look at a photo of his wife and child. He is interrupted by the arrival of Iris who congratulates him on his beautiful family. Ryan tells her that she is not like her, and he is a normal human being. Iris informs him that she is also a regular human being. The doctor notices her ring and asks if she doesn't also want to be with her husband. She mentions that her husband is not like them, and he is a hero. But it is them, who reminds the heroes what they are fighting for. He mentions his daughter, and Iris asks if he wants to hold his daughter knowing he did everything he could. He reluctantly agrees as Ray and Ralph come to stand behind her. Ray tells Iris that Lois just informed them that six more Earths have van to come with them.

Iris reminisces saying goodbye to her husband back on the Waverider. The two shared a tender goodbye, both believing it might possibly be their last. Barry promises Iris that no matter what he will always come running home to her.

Earth-1 - Waverider Lois Lane is watching a monitor and is devastated to watch Earth-73 be destroyed by the wave. The Monitor is beside her and she informs him that there are only seven remaining worlds. Lois brings up how ironic the situation is, the biggest event in history to ever happen and no one will ever read the story. The Monitor brings up how these Earths were not the only ones destroyed, his world also died and he lost his family. He reminisces his life and how they meant everything to him. He now wishes he had spent more time with them and not been so focused on his work. They are interrupted by Superman returning from somewhere. He smashes his fist down against the floor, devastated at having not been able to save what was most likely Earth-73. She asked her husband's counterpart if he wishes to take a break. He ignores her and begins a speech about why he wears his family's crest, because it is to save people, and that he would never give up fighting. Lois asks why he turned the blue that used to surround the 'S' into black. He tells her it is because even in the darkest times, hope cuts through. "Hope is the light that lifts us out of the darkness." he asked to be sent back, to another Earth to try and save them. He disappears and Lois comments on his bravery, only to realize The Monitor has also disappeared and she is alone.

Earth-1 - Waverider Supergirl is in the ship's office looking at the Book of Destiny, debatably getting ready to open it. She is stopped by Kate. Her friend asks her what she is doing, and Kara insists she has to do whatever she can to bring her world back, and all the other worlds and she can fix it. Kate insists that is not the answer, Kara is thoroughly becoming more annoyed and asks what else can be done. She can't stand by while all those people are dying. Batwoman says she doesn't like it, but using the book will destroy her. Supergirl says it's what she has to do, and Batwoman says that she will stop her. Kara promises that Kate will not be able to. Kate is unsure how she would bear in a fight even with the kryptonite, and tries her best to talk her friend down. Rationalizing that if she does this and it doesn't work they can't risk having something happened to her because she is the Paragon of Hope, and without her, they will all be doomed. Annoyed at her reasoning, Supergirl reluctantly leaves. Kate lets out a breath of air she didn't realize she had been holding.

Later Kate takes a moment to track down Kara. Telling her she understands why Kara wanted to bring those people back, and how she has the biggest heart of anyone she's ever met, but she can't get hurt, it would open them to danger. Kara complements her for being the Paragon of Courage, admitting it took a lot to stand up against a Kryptonian. Kate sees how good of a person Supergirl is, and decides to give her the Kryptonite that she took off Bruce. Believing her friend is a good person, Kara tells her to keep it and that she "[has] the courage that [Kate]'ll never have to use it"

Both Supermen and Lois Lane are in the controlled rooms when they are surprised to find John Constantine, Dig and Mia all appear before them. They are defeated and say Oliver would not come back with them. Dig apologizes to Sara and asks how everyone else did. They are told how Barry was able to stop that antimatter, and Earth-1 is all that remains.

In another room Barry Allen finds Jefferson. He tries to console him, but he believes nothing is going to be okay again. The Flash tells them how Earth-90's Flash died, and he coincidentally looked exactly like his father Henry Allen. A man who was imprisoned for most of Barry's life after one of Barry's enemies framed him from murdering his mother. Jefferson opens up about his father Alvin Pierce was also a good man and a reporter. But he was murdered by Tobias Whale when he was 12. He made sure to carry on the lessons his father taught to his children. They agree that neither of their fathers were quitters, so they must honor their memories and "rage against the dying of the light". Having first had a rocky start, the two men shake hands and re-introduce themselves with their full names.

The Waverider announces Iris, Ralph and Ray have returned with Dr. Choi. Iris runs to her husband, relieved he is alive. Barry tells her that, Allen from Earth-90 sacrificed himself. Iris isn't all that phased, as long as she has her husband. They introduce everyone to Black Lightning who immediately takes note of both Supermen and is astonished that they are not just stories. They also announced they have the paragon of humanity and introduce Ryan, as he is going to help them save the world. Jefferson and Dig briefly locked eyes with a nod of acknowledgment at each other.

Now that everyone is back together, they began discussing, what to do next, but are interrupted with the arrival of Lyla. She appears before them and Dig immediately goes to hug and kiss his wife. She tells them with all the worlds disappearing her powers were not working how they should be, she also admits she doesn't know where exactly she has been. Team Flash is concerned why the Anti-Monitor would want Harbinger back on the ship, as he's possibly been controlling her the entire Crisis. They become further concerned when Pariah appears, as he is only to arrive before great tragedy.

The Harbinger turns around to everyone with her eyes glowing white. She is possessed by the Anti-Monitor and announces "It's time to end the age of heroes and everything you hold close" before throwing Dig against a wall. Superman and Black Lightning both try to fight her, but are both quickly overpowered. Not wanting to waste anymore time, the anti-Monitor forces everyone to the ground unable to move. There he tells Novu how foolish he has been for trying to stop him. The Monitor tells Mobius it was foolish to allow his creation in the first place. The two begin to attack each other with their power in the form of bright energy being forced in the other's direction. Unfortunately, Mobius wins and is able to destroy Novu, and take his powers. However, before he dies Novu is able to tell Pariah, that he will know what to do when the time comes.

The Waverider interrupts them with an alert that Earth-1 has been destroyed. The Anti-Monitor quotes that he will be victorious in a matter of seconds. The Waverider informs them that they have exactly 28 seconds. In that moment, Pariah realizes what he must do. Before that wave can hit them, he vanishes the seven Paragons away. J'onn tries to alert everyone before he too is banished, followed by Sara in the med bay beside Oliver's body. Pariah proudly announces that he has sent them away. Superman, Lois, Black Lightning, Iris, and Ralph all remain on the ship determined to go down standing. Before disappearing Superman gives a final nod to Iris, still believing everything is going to be okay.

Vanishing Point Batwoman and Superman find themselves close together both wondering where they are. Sara explains they are at the Vanishing Point. A point outside of space and time. She remembered from her last visit many years earlier, it was still destroyed from when Leonard Snart blew it up. They all quickly realize Pariah sent them there knowing the anti-Monitor could not follow. Barry begins to panic, telling everyone they have to go back, but he is stopped when Superman starts to have red glowing shards coming from his body. He feels something is wrong, while Supergirl holds him, begging him not to leave. He disappears and is replaced by Lex Luthor to everyone's horror. He exclaims how happy he is that his plan work, and he replaced Superman as the "Paragon of Truth." Admitting he had the Book of Destiny and decided to write his name in over Superman's. He is now one of seven people in the entire universe that is left. All seven paragons are trapped together.

Production
Shooting for began on September 24, 2019.
 * During production, the episode was titled "Crisis on Infinite Earths: Hour Three".

Behind the scenes

 * Cress Williams became immediately starstruck when he stepped onto the set of the Arrowverse's forthcoming Crisis on Infinite Earths saga for the first time. "It's like going to a new school", says Williams, who took a break from shooting Black Lightning in Atlanta to spend a week working on the crossover in Vancouver. "I was just really overwhelmed at the pure number of people, and all of these super suits. I was working with the Flash, two Supermen, most of the cast of The Flash, and some Arrow people. It was just a real hodgepodge, a full room".
 * For Guggenheim, it was important that Black Lightning appeared in the crossover for more than a glorified cameo, with Williams flying between the two filming locations on the weekends to maximize his availability while Black Lightning 's writing staff reduced his role in several episodes to better accommodate his involvement.
 * Marc Guggenheim noted that the inclusion of Cress Williams' Black Lightning was a particularly challenging one due to the actor having to fly back and forth from Atlanta (the primary filming location for Black Lightning) to Vancouver (where Crisis was filmed). To make things even more difficult, logistically, Williams' costume, specially modified to give off a pulsating electric aura, was expensive to transport between the two filming locations to accommodate Williams' series and the crossover. "His costume is a very involved piece of equipment that has to be traveled (and) has a separate handler that has to travel with it", explained Guggenheim in an interview with Variety. "It was suggested to me at one point, by one of the money people, "Does Black Lightning really have to wear his costume in the crossover?". He has to wear that costume. It just wouldn't be the same if he didn't".
 * Other Arrowverse actors were jealous of the way the mask Cress Williams wears as Black Lightning fits on his face. The mask goes on with the crew gluing magnets to the actor's face, allowing him to remove the mask, which has magnets in it, between takes. 's jaw dropped when he saw this, informing Cress that when the crew puts his Elongated Man mask on, it's glued to his face; so he has to wear it all day, and that there's no other way they could make Ralph's mask work.

Trivia

 * When Barry came back to Iris, he stated that he told her that he'd be running home to her which is a reference to "Runnin' Home to You", the song he proposed to her with.
 * This is the second time a character makes a sacrifice to save another character who is destined to die in a possible future. The first was H.R. Wells who sacrificed his life to save Iris by trading his life with her by getting killed by Savitar, and the second is Barry Allen (Earth-90) who trades his life with Barry Allen (Earth-1) to stop the anti-matter from destroying Earth-1.
 * When absorbing the energy from the antimatter cannon, Jefferson quotes his school's motto.
 * This is the first time since that a version of Tina McGee has appeared in the Arrowverse, albeit via archive footage from the 1990  series.
 * The clip shown as Barry's memory when running to disable the antimatter cannon is a scene from the episode.
 * Frost says it's Ralph's first crossover, breaking the fourth wall as it's actually Hartley Sawyer's first-ever crossover outside a brief appearance in.
 * Ralph's reaction to seeing the assembly of heroes, "Holy All-Star Squadron", is a reference to the All-Star Squadron, a World War II era offshoot of the Justice Society of America in the comics.
 * Tom Ellis recorded his cameo in the crossover right before production on Lucifer's fifth season commenced.
 * Lucifer mispronounces Constantine's name with the correct pronunciation of the name in the original comics, a shout-out to fans after it was changed in the television and film adaptations of the character.
 * Earth-666 contained a billboard as a nod to the DC graphic novel Watchmen that was airing its TV adaption at the time. Thankfully, Marc Guggenheim got permission from Watchmen show-runner Damon Lindelof to use it.
 * Likewise, billboards for Supergirl appeared in a few Lucifer episodes.
 * Kara holding Earth-96 Clark as he dies mirrors the iconic Dan Jurgens spread from the Death of Superman story in Superman #75.
 * The scene was previously referenced in with news footage of Lois Lane's Earth-75 doppelgänger mourning Superman-75.
 * It's also a reversal of the cover of Crisis on Infinite Earths Vol. 1's seventh issue Beyond the Silent Night. On the cover, Superman is holding a dead Supergirl.
 * Dina Meyer reprised her role as the Barbara Gordon/Oracle of Earth-203 in an uncredited voice cameo during the cold open.
 * At the end of the episode, the few surviving characters are alike in a few ways:
 * Kara, J'onn, and Lex are the last survivors of Earth-38's Krypton, Mars, and Earth respectively.
 * Kara and J'onn are the only survivors of the Superfriends.
 * Barry is the last survivor of Team Flash.
 * Sara is the last surviving member of both the Legends and Team Arrow.
 * Sara and Lex have each been resurrected from the dead at some point.
 * This is the last episode of The Flash to centrally take place on Earth-1, as subsequent episodes happen post-Crisis, and are set on Earth-Prime.

Goofs

 * The multiverse was still getting erased despite the antimatter cannon being disabled; Flash of Earth-90 said all remaining Earths would be destroyed in one go thanks to a fail-safe, not one-by-one.
 * If Pariah could teleport people, why didn't he send all the heroes and not just the Paragons to the Vanishing Point?
 * The first 5 seasons of had a newspaper detailing on how the Flash "vanished" in the crisis. As of, it was the Flash of Earth-1 while fighting the Reverse-Flash with a group of heroes. However, the Flash of Earth-90 vanished through destroying the Anti-Monitor's cannon. This is likely due to the numerous timeline changes leading up to the current version of Crisis.
 * The out-of-universe explanation is as Marc Guggenheim said: "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. 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."
 * Leonard tells the heroes they have 28 seconds from the destruction of Earth-1 to the destruction of the Waverider, but the gap is actually 45 seconds. However, it's possible there was some time overlap during the transportation of the Paragons to the Vanishing Point.
 * When Black Lightning arrives in the Nexus, he is confused when Pariah tells him about the multiverse. However, Gambi previously told Black Lightning about the multiverse in, which features the Crisis reaching Jefferson's Earth, thereby setting up his appearance in this episode.
 * However it is possible Jefferson was only convinced of such as of this episode.