On Earth-90, the heroes of that world have been soundly defeated in an epic battle, and only the Flash of Earth-90 (a doppelganger of Earth-1's Henry Allen & Earth-3's Jay Garrick) survives to witness the Monitor collect a strange, ancient book and promise that "all of you will perish". The Monitor travels to Earth-1 and delivers the book to Dr. John Deegan, a psychiatrist with controversial theories about leveling the playing field between ordinary people and super-people; Deegan is encouraged to use the book's power to remake reality and "think big".
As the world is plagued by red skies and yellow lightning, Oliver Queen wakes up...in Barry Allen's home. With Barry's superpowers. And with Barry's wife, Iris, who calls him "Barry" and doesn't notice anything amiss. Cisco calls in with a situation, so Oliver haphazardly suits up as the Flash and stops a gang of thieves at Ivo Labs. Doing his best to convince Team Flash that nothing's amiss, he speeds over to Star City, where Barry has similarly woken up in Oliver's life and with all the skills of the Green Arrow.
The two return to S.T.A.R. Labs and try to convince Team Flash of the switch, but they're skeptical and decide to lock Oliver and Barry in a pipeline cell. Barry hits on the idea of traveling to Earth-38 and enlisting Kara Danvers' help, so to escape their cell, Oliver coaches Barry on dislocating his thumbs to escape handcuffs, and Barry coaches Oliver on phasing through solid objects. Iris catches them escaping, but Barry convinces her of their true identities, and she helps them steal an inter-dimensional extrapolator and breach out.
On Earth-38, Kara is visiting Clark and Lois at the Kent farm in Smallville, looking for support after recent events. Clark also has something important he wants to talk about, but they're interrupted by the arrival of Oliver and Barry, who Kara recognises as their real selves. Oliver and Barry try to do some training, reminiscent of their first crossover, but they get in a heated argument and all Oliver manages to prove is that being the Flash requires more skill than he gave credit for. Eventually they patch things up and speak about their respective superhero experiences: Barry needs his joy and optimism to tap into the Speed Force, while Oliver needs his rage and pain to endure and be the Green Arrow; if they're going to be heroes while their identities are swapped, they need to act like one another.
Back on Earth-1, the red skies and yellow lightning are getting worse, and Cisco starts getting half-formed vibes of the Monitor, which convinces the team that Oliver and Barry's switch might be real and part of something larger. Meanwhile, at Ivo Labs, Oliver's heroics accidentally activated a prototype ARGUS battle robot called "A.M.A.Z.O." which goes berserk and starts attacking the city. Ralph and Killer Frost try to stop it, but A.M.A.Z.O. is able to absorb and mimic their powers. Cisco breaches to Earth-38 and convinces Oliver, Barry, Kara and Clark to return with him and help stop A.M.A.Z.O.
Though the fight initially goes well, A.M.A.Z.O. is able to copy the Flash, Supergirl and Superman's powers, making him practically unstoppable. Sherloque suggests dealing with A.M.A.Z.O. like any machine — simply turn it off — and Iris realises that if A.M.A.Z.O. copied Supergirl and Superman's powers, it likely copied their weakness to kryptonite as well. While Supergirl and Superman hold A.M.A.Z.O. down and the Flash nullifies its phasing, the Green Arrow uses a kryptonite-tipped arrow to deliver a virus and shut it down.
While the day is saved, Iris worries that in order to be the Green Arrow, Barry will become too much like Oliver. Clark returns to Earth-38 while Kara remains to help Oliver and Barry return to normal. Cisco vibes the Monitor and sees him meeting with Deegan, but the Monitor is powerful enough to sense Cisco and warns the heroes to give up. Oliver recognises the skyline behind the Monitor and Deegan, and announces their next destination: Gotham City.
And in Gotham, a certain bat-themed vigilante is patrolling the rooftops, watching over the city...
Examples:
- Ascended Meme: When trying to goad Barry, Oliver bets he can't go more than nine hours without hearing "some SAPPY motivational speech."
- Actually Pretty Funny:
- Barry's clearly enjoying the switch, much to Oliver's irritation — at least, until Oliver lets it slip that he woke up next to Iris.
- After Barry dislocates his thumb to escape his cuffs, Oliver starts laughing because he's never realised how ridiculous a dislocated thumb actually looks.
- All Your Powers Combined: A.M.A.Z.O. eventually assimilates powers from Ralph, Killer Frost, the two Super-cousins and the Flash.
- And I'm the Queen of Sheba: When Barry and Oliver try to convince Team Flash of their switch, Cisco sarcastically says he's Wild Dog. Sherloque takes it literally.
- Arbitrary Skepticism: Given all the insanity they've seen over the last five years, from time travel to alternate Earths, you'd think Team Flash would be more open on the idea of Barry and Oliver switching identities. Instead, they're convinced the duo are either mind controlled or replaced by impostersnote and lock them up. They eventually come through, citing this trope.
- Assimilation Backfire: Iris guesses that A.M.A.Z.O. inherited the weaknesses of the copied people alongside their powers, so the heroes decide to shoot him with Kryptonite.
- Big "WHAT?!": Oliver's reaction when Barry takes a photo of him with Barry's arrows in his back for comedic posterity.
- Blessed with Suck: Much to Oliver's chagrin, his newfound powers means he cannot drown his sorrows through regular alcohol.
- Borrowed Catchphrase: Barry uses a few of Oliver's lines.
- Both Sides Have a Point:
- Barry shooting Oliver in the back with automatic crossbows, literally jumping up and down with laughter, and taking a photo might come across as an In-Universe Catharsis (especially since his Healing Factor means it won't last for long at all)...but it also makes him out to be a real dick. Oliver even points out that he shot Barry to teach him a lesson. Barry shot him just for shits and giggles.
- While Oliver has every right to be upset at Barry for shooting him in the back and playing around given their current situation, the lengths he goes come across as a bit too whiney and even downright mean when he basically tries to insult Iris, casts aspersions on the idea of Barry training at all (which implies that Barry doesn't work hard), and as Barry points out he handled the time Oliver shot him way more gracefully. He also points out that Felicity does as much quarterbacking by herself as Team Flash put together.
- Brick Joke: Barry has never quite forgiven how Oliver shot him four years ago during a training session and is very gleeful to get some payback.
- Broken Pedestal: Iris reveals to Oliver that Felicity feels this way about him after he went to prison.
- Call-Back:
- Like when Barry was imprisoned in Iron Heights, Barry relies on a toilet to escape, although this time he does not use an acid.
- Barry shoots Oliver the same way Oliver shot him in Flash vs. Arrow, that is, tricking him with secret automatic crossbows while distracting him with an Arrow Catch.
- The Kryptonite arrow is brought up again after Crisis on Earth-X, although it is more important in that it is the one weakness of A.M.A.Z.O.
- The construction site where Oliver leads A.M.A.Z.O. to looks extremely similar to the one in Crisis on Earth-X.
- When the three supers pin down A.M.A.Z.O. so Barry can fire off his kryptonite-virus arrow, Oliver puts the android in a chokehold similar to the one he pulled on Barry in Flash vs. Arrow.
- In Season 1 of The Flash, Iris mentioned that she and Eddie had an agreement where if they each got propositioned by one of three people, the other would understand if they gave into the temptation. Because of the switch, Iris gets to marry her dream guy, the physical attractiveness of Oliver Queen and the emotional attractiveness, as far as she remembers, of her Barry Allen.
- Also in Season 1, Felicity compared dating Ray Palmer to dating "Barry in Oliver's body." She doesn't seem to think it's as fun now, though.
- Chest Insignia: A.M.A.Z.O. signifies a new power he assimilates with one representing each person he copies it from.
- Comically Missing the Point: After the initial shock, Barry geeks out on the possibilities of how they switched.
- Conflict Ball: Team Flash's sudden refusal to believe that Oliver and Barry switched lives and imprison them is used to motivate them to seek Kara's help and shoehorn her into the plot.
- Curb-Stomp Battle:
- A.M.A.Z.O. utterly trounces Elongated Man & Killer Frost.
- A.M.A.Z.O. versus Supergirl, Superman, Flash, and Green Arrow. Until it copies their abilities, the android doesn’t manage to get a single hit in.
- Damn You, Muscle Memory!: When Oliver (in the Flash uniform) confronts the bad guys in the beginning of the episode, he naturally reaches back for an arrow that isn't on his back anymore.
- Didn't See That Coming: Due to his lack of familiarity with fighting speedsters, Clark gets thrown in for a loop when the A.M.A.Z.O. android uses the powers it copied from Oliver to phase itself to avoid his punches.
- Distinction Without a Difference: Barry objects to Oliver calling the Pipeline a prison — it's a special tube that dampens metahuman powers.Barry: OK, it's a prison.
- Do I Really Sound Like That?: Oliver's amused reaction to Barry imitating his lines.
- Dude, Not Funny!: Oliver does not find Barry's revenge on him funny at all, since his superhero experience has been awful.Barry: Come on, man. I was a much better sport when you shot me.
Oliver: I shot you to teach you how to case an environment. You shot me to get a laugh! - Emotional Powers: Barry and Oliver draw on opposite emotions to use their powers/skills, so they have to behave like each other in order to use their swapped gifts properly. Oliver needs to access joy and contentment to fully control the Flash's speed, while Barry needs anger to tap into the Green Arrow's extraordinary athletic and combat abilities.
- "Eureka!" Moment:
- When Oliver mentions how nobody on Earth believes them, Barry gets the idea to go to Earth-38 and see if Kara still remembers them.
- Barry and Oliver realize they have to act like each other if they want to make the best of the situation until they can switch back to normal.
- Eye Scream: Barry's arrow shoots straight into one of A.M.A.Z.O.'s eyes.
- Foreshadowing:
- The break-in at the beginning being set at an Ivo warehouse. As soon as the heist is averted, a broken crate reveals the A.M.A.Z.O. android.
- Ralph compares A.M.A.Z.O. to Gort in his capability as a robot to destroy everyone. Whoever the Monitor is, his motives for giving a man the power to reshape reality seems to be a similar evaluation of humanity by advanced alien beings, as he declares Earth-90 had failed in the use of it.
- "Freaky Friday" Flip: Barry immediately guesses this might have happened between him and Oliver, even saying "Freaky friday". They soon realize it's more complicated than they thought.
- Fun with Acronyms: A.M.A.Z.O. stands for Anti Meta-human Adaptive Zootomic Organism. Cisco lampshades how it reads, and approves of the name.
- Gone Horribly Right: As far as Iris is concerned, Barry takes Kara's advice to be the Green Arrow a little too well; she doesn't like what she sees during the battle against A.M.A.Z.O. and is afraid of Barry losing himself.
- Hypocrite: Oliver accuses Barry of not taking the amount of training it takes to be the Green Arrow seriously, but at the same time takes Barry's powers for granted and scoffs at the idea that Barry actually trains. He also mocks Barry for having Iris in his ear when he’s in the field, only for Barry to point out that Oliver's had Felicity doing the same thing for even longer.
- I Can See You: The Monitor can see Cisco when he is vibing him.
- Innocently Insensitive: Oliver doesn't take kindly to Barry using his archery skills lightly, considering the five years of hell he spent on Lian Yu (and sometimes elsewhere) developing them.
- In-Universe Catharsis: Barry's glee at getting revenge at Oliver for that training session the latter put Barry through four years ago. He really relishes the moment.
- The Juggernaut: After adapting their powers, A.M.A.Z.O. kicks the crap out of the four heroes and they need to use strategy to take him down.
- Laser-Guided Karma: After accusing Barry of taking the skills of the Green Arrow for granted, Barry winds up putting Oliver on his back without much effort.Barry: If you really knew how to use my speed, I wouldn't have been able to lay a finger on you.
- Leaning on the Fourth Wall:
- Upon waking up in Barry's life, Oliver's first response is to blame Barry, just as the fans always do. However, it's Not Me This Time.
- While at S.T.A.R. Labs, Oliver ducks out into the hallway...before immediately realizing the others were about to follow him out there, since they could tell something was up. In other words, the show telegraphed the hallway scene.
- As part of his Drill Sergeant Nasty mode to get a rise out of Barry, he tells him how he can't go nine hours without Iris giving him some sappy motivational speech, something fans have been complaining about for years.
- When Cisco says reality was switched by 'some guy with muttonchops', Ralph says "Man, it's not even Tuesday." Guess which day The Flash normally airs?
- Oliver complains about there not being a toilet in the pipeline cell, something fans have been wondering about since nearly the beginning of the show. Barry finally provides the answer by revealing a toilet that slides out from the wall.
- Locked Out of the Loop: Oliver apparently hasn't checked up with Barry since he got out of prison. He has no idea who Cicada is or anything else he's been going through.
- Mad Doctor: John Deegan gets apparently fired from his workplace because he wants to conduct eugenic experiments with psychiatric patients (he even gets called Frankenstein).
- Mundane Utility: Lois and Clark are introduced with the latter casually holding up a truck with Super-Strength so the former can work on it. Kara uses her own strength to open beer bottles with her thumbs.
- My God, You Are Serious!: Oliver laughs when Barry tells him to call Iris his Lightning Rod. He then realizes that he means it and refuses.
- Mythology Gag: Several, including:
- The first scene of Earth-38 is an establishing shot of the Kent farm, set to Remy Zero's "Save Me" — and even starts at the same point as Smallville's Season 5-10 opening title sequence.
- After Clark offers to return to Earth-1 along with Kara to assist with the problem there, he explains that he is "A friend".
- The final shot of the episode, with Batwoman standing on top of the Wayne Enterprises building, looks a lot like the final shot of the opening of Batman: The Animated Series.
- Nice Job Breaking It, Hero: Oliver accidentally boots up A.M.A.Z.O. when he overcharges his lightning fighting the diamond thieves.
- Not Me This Time: Oliver's first assumption on finding out he's the Flash is to automatically assume that Barry has been up to some time/reality warping shenanigans again. But Barry is just as clueless as Oliver is.
- Not So Invincible After All: Copying powers and being Immune to Bullets makes A.M.A.Z.O. scary, but after Iris' thinking creates the idea that Kryptonite is the solution, the kryptonite arrow destroys A.M.A.Z.O. completely.
- Oh, Crap!: Clark's reaction when A.M.A.Z.O. evades his punches by vibrating its body.
- Oh, No... Not Again!: Once Ollie comprehends the situation he's in at the beginning, he exasperatedly thinks Barry may have messed with time again. Caitlin later makes the same assumption.
- Once More, with Clarity: The Stinger previously seen no less than three times is shown again!
- Poke in the Third Eye: Much like Zoom and DeVoe before him, The Monitor can tell that Cisco is vibing him and speaks to him directly, ultimately giving him a Psychic Nosebleed for his efforts.
- Power Incontinence: Obviously, Oliver is not used to Barry's powers. Similarly, Barry has to adjust to Oliver's skillset.
- Punch! Punch! Punch! Uh Oh...: After A.M.A.Z.O. copies the powers of the two Supers and the Flash, Superman decides to try punching him again, only for A.M.A.Z.O. to phase through every punch. Superman notes this may prove to be a problem before A.M.A.Z.O. smacks him aside.
- Really Gets Around: Turns out Sherloque has an ex-wife (his third, to be exact) on Earth-38! He has Clark deliver an alimony check for him.
- "The Reason You Suck" Speech: Iris indirectly gives one to Oliver, since she was still of the belief that he was Barry: she says that she could never love Oliver because he's filled with hate and vengeance and because of what he did to Felicity by cutting a deal with the FBI behind her back; she was basically Felicity's support during Oliver's imprisonment.
- Red Sky, Take Warning: One of the signs something is wrong is red skies and lightning.
- Reflexive Response: Oliver instinctively makes it like he was reaching for his bow during a fight.
- The Reveal: The pipeline's cells do have toilets - they're just hidden in the walls.
- Running Gag: Once again Diggle vomits when transported by super speed.
- Sequel Hook: The episode ends with Cisco, Barry, and Oliver seeing a vision of the Monitor giving Dr. Deegan the book...and then the Monitor talks back. Oliver recognizes the skyline as Gotham thanks to Wayne Tower.
- Serious Business: Barry's glee at the situation evaporates when Oliver tells him he woke up with Iris by his side.
- Shirtless Scene: Oliver wakes up shirtless at Barry and Iris' loft.
- Shout-Out:
- Ralph compares Amazo to Gort.
- Cisco calls him T-3000.
- Barry and Oliver's situation is compared to Freaky Friday and Quantum Leap.
- Single Woman Seeks Good Man: Played for drama; Iris' love for Barry partly comes from his kindness, but the "Freaky Friday" Flip has caused some problems in her marriage. Iris sees Oliver as a vengeful man and is seeing how Barry is becoming too much like him.
- Snark-to-Snark Combat: Clark and Lois trade some playful snide remarks with each other.
- Something Only They Would Say: Barry revealing the words he said to Iris when he first came to the West household after his dad was arrested is what convinces her that he and Oliver are telling the truth.
- Special Edition Title: Less elaborate than the Crisis on Earth-X one; the regular logo shows up only to be replaced with "Elseworlds".
- Stating the Simple Solution: Since A.M.A.Z.O. is a computer, Sherloque states that they should just turn it off, giving Cisco the idea to develop a virus.
- Stock Footage: The destruction of Earth-90 is shown for the fourth time now.
- There Is No Kill Like Overkill: Cisco calls out Oliver when he uses a lightning throw to deal with a few ordinary robbers.
- Too Fast to Stop: Oliver has some problems controlling his speed at first. He misses the warehouse by a few blocks when trying to stop the diamond thieves and slams into a wall in a failed attempt to hit one of them.
- Unwitting Pawn: Dr. Deegan is this to the Monitor, who gives him a book that makes him a god.
- Wham Shot:
- Red skies and yellow lighting.
- The episode ends with a shot of Batwoman.
- What the Hell, Hero?: Oliver becomes increasingly frustrated with Barry for making light of the situation, finally snapping during the training scene on the farm.
- Worthy Opponent: Subverted, the Monitor is impressed by Cisco's vibe powers...only for him to then go on how the heroes stand no chance against him.
- You Fight Like a Cow: Oliver tries to get a rise out of Barry this way. It doesn't work.
- You Have to Believe Me!: Team Flash won't believe Barry and Oliver's story how they've changed places. At least not until Barry tells Iris something intimate that nobody else would know. And then Cisco starts having visions of the Monitor plus the red skies.
