The episode was previously titled "Elseworlds: Hour Three".
Barry breaks the fourth wall in this episode; he says "this has gotta be the craziest thing you've heard in the past three hours"; a reference to the fact that the Elseworlds crossover is split into three hour-long installments.
The opening monologue in this episode was narrated by John Deegan. But for the last line, he says it after transforming into Superman.
Near the end, Deegan's face is shown disfigured in black and white almost like a skeleton, similar to his comic counterpart's appearance.
When John Deegan becomes Superman and rules the earth, this is a reference to the plot of the video game Injustice: Gods Among Us where Superman is a tyrant that rules the earth.
When Deegan fought Superman in a building, a civilian calls him Bizarro. This is a nod to the fact that a lot of people didn't like that Bizarro was a girl in the Arrowverse and wanted a male version.
In the comics, Doctor Destiny is associated with Dreamstone, artifact created by Dream of the Endless, while his Arrowverse counterpart uses Book of Destiny, artifact created by Dream's older sibling Destiny.
When Barry and Oliver are looking for Cisco, Barry references the season 3 premiere Flashpoint when he rewrote reality and Cisco wasn't much help.
Kara correctly guess Lois and Clark are having a baby, a reference to Jonathan Samuel Kent, who first appeared in DC Comics' Convergence event in the miniseries Convergence: Superman #2 (July 2015). Jonathan is the biological firstborn son of Superman/Clark Kent and Lois Lane and is half kryptonian/human
Gary says Oliver and Barry are his heroes, "Legends", a reference to Legends of Tomorrow who are not part of the annual crossover this year, unlike the previous two years.
While in the Fortress of Solitude, Superman presses a piece of coal into a diamond to put it in a ring and propose to Lois Lane, resembling Smallville's 100th episode ("Reckoning"), when Clark Kent did the same to propose to Lana Lang. The aforementioned scene itself is a reference to Superman III, when Superman presses a piece of coal to give Lana Lang a ring after she tells him she has to sell hers.
Superman says to John Deegan as Superman, "doctor can I have a word", a similar quote to Superman II, when he says to Zod, "General, would you care to step outside?"
Furthermore, it resembles Kara's quote to Overgirl in"Crisis on Earth-X, Part 4""" to lure the evil doppelganger into a fight.