When Barry Allen and Oliver Queen wake up one morning and realize they have swapped bodies with each other, the two set off to find out what disturbed the timeline to cause such a shift. However, things quickly go from bad to worse when they present their case to Team Flash and the gang doesn’t believe them. Barry and Oliver realize they need Supergirl's help and travel to Smallville on Earth-38 where they end up meeting Kara’s cousin, Clark Kent, and intrepid reporter, Lois Lane.
This is also the only episode of Season 5 not to feature Nora.
The episode was previously titled "Elseworlds: Hour One".
The episode's title is listed as "Elseworlds: Hour One" on Netflix in Canada and Israel.
After Barry and Oliver switch lives, Barry refers to it by saying "Man, what a total Freaky Friday. No, wait, we didn't switch bodies. It's more of a Quantum Leap". In the Freaky Friday franchise, the characters' minds swap bodies. In the Quantum Leap TV series, Dr. Sam Beckett changes places with people when he's still in his own body but people perceive him to be the other person, which is closer to their situation.
Noticeably, despite Barry obtaining Oliver's more muscular build from inheriting his life, Oliver did not obtain Barry's slim frame, but rather remained the same.
A major Smallville easter egg appears in this episode where the show's theme song "Save Me" by Remy Zero was played during the introduction of the Earth-38 Smallville, with the farm location featured in Smallville also reused. In addition, the Smallville version of Green Arrow's suit appeared in the opening scene on one of the corpses of the Earth-90 heroes killed by the Monitor.
Lois calls Clark "Smallville", referencing Clark's nickname given to his comic book counterpart by Lois Lane.
When Barry tried to talk like Oliver, he said "wear a mask", which is what Oliver said to him in "Pilot".
The scene when Barry shot Oliver with arrows is almost an exact replica of the original scene from "Flash vs. Arrow", with Barry and Oliver switching dialogue and roles.
The shot that shows the remote control bows is recycled from that episode, with only a few changes through edits.
When Oliver is about to faint, Iris says "Nanites, courtesy of Ray Palmer", the same quote Oliver said to the Reverse-Flash in "Rogue Air", which became an internet meme after that episode's airing.
When Team Flash realizes something weird's going on, Ralph says, "Man, it's not even Tuesday". This fourth-wall-breaker is a nod to the fact that episodes of The Flash typically air on Tuesday nights, but that the show swapped time slots with Supergirl, instead airing on Sunday night, for the Elseworldscrossover event.
After Barry shot him with arrows, Oliver complained that Barry can't solve any problem without Iris giving him a motivational speech. This is a reference to a real-life complaint from fans of the show, that in most episodes Barry isn't able to solve a problem until Iris gives him a speech on comms.
Referencing A.M.A.Z.O., Ralph says "So an evil copycat Gort is coming to klaatu barada kick-to our asses". This line is a reference to the 1951 film The Day the Earth Stood Still and its character Gort, also using the phrase "klaatu barada" from it.
During the same conversation, Cisco refers to the situation by saying "How do you stop a T-3000 that kills for breakfast?", which is a reference to the popular Terminator franchise.
When the Flash was distracting A.M.A.Z.O., the chase leads to a scaffolding area, which bears resemblance to where the Prism was located during "Crisis on Earth-X, Part 2".
When Cisco asks who Clark is, Clark replies "A friend", referencing the 1978 film and the first feature length adaptation of the Man of Steel himself, Superman.
A part of the Super Friends intro plays when Clark does the infamous Superman "S" reveal.
The super-speed sketch Oliver made of the Monitor and John Deegan was drawn and provided by DC artist Jim Lee.
When Barry and Oliver meet Clark, Barry asks the Oliver if he's puffing out his chest, to which Oliver agrees. In the original script, Oliver was instead supposed to say "no".
According to Barry, A.M.A.Z.O. can't run and phase at the same time, although there were countless instances on the show where speedsters phased through walls while running; including Barry when he first learned to phase in "Tricksters".