One of the songs played right before the wedding ceremony is Joseph Haydn's "Gott erhalte Franz den Kaiser", also known as "Kaiserhymne", an anthem to Francis II, Emperor of the Holy Roman Empire, which would later become the anthem of Austrian Empire and is the tune of the "Deutschlandlied", the national anthem of Germany, used by the Weimar Republic, Nazi Germany and the current Federal Republic of Germany.
This is the first episode of Supergirl to centrally take place on Earth-1. It is also the first time Alex has appeared in a crossover as she was absent (off searching for her father) when Kara met Barry for the first time in "Worlds Finest" and was not involved with the Invasion! and "Duet" crossovers.
At the beginning of the episode, after Kara defeated a Dominator, she said that the Dominators are "so last year". This is a reference to the previous year's crossover, Invasion!, in which the Dominators served as the main antagonists.
Martin synthesizes a way for Jax to retain superpowers, albeit not his original ones. When he describes them, Jax suggests that Stein's trying to turn him into the Marvel superhero Spider-Man. He questions whether he'll have Spidey-Sense, but Stein tells him he won't, mockingly calling himself "the Spectacular Sticky-Man".
The music that plays during Barry and Iris's rehearsal dinner is the same music played in the episode "Green Arrow" when Oliver is about to propose to Felicity.
When Barry asks Kara for a favor, he references the events of "Duet".
The song Kara sings is "Runnin' Home to You", the very same song Barry sang to Iris when he proposed to her, previously sung in "Duet".
William Katt cameos as the ill-fated minister who oversees Barry and Iris' wedding. Katt is best remembered for starring in the comedic superhero series The Greatest American Hero in the early 1980s.
The resistance members at the start of the episode are seen carrying AK-47 assault rifles, which would not have been developed since the USSR had already been destroyed, and would not have had the capacity to reverse-engineer the German MP-44.
Dark Arrow fires green arrows at the scientist, but he only carries red arrows.
Barry and Iris were supposed to use "Runnin' Home to You" as their first dance, but was used as the bridal chorus for the episode. However, Barry and Iris may have simply changed their minds between their initial decision and their actual wedding.
Crisis On Earth-X Sizzle The CW
Supergirl 3x08 Promo "Crisis on Earth-X, Part 1" (HD) Season 3 Episode 8 Promo - Crossover Event
DCTV Crisis on Earth-X Crossover Cast Teaser - The Flash, Arrow, Supergirl, DC's Legends (HD)
DCTV Crisis on Earth-X Crossover Cast Tease 2 - The Flash, Arrow, Supergirl, DC's Legends (HD)
Supergirl Inside Crisis on Earth-X - Supergirl The CW
DCTV Crisis on Earth-X Crossover Behind the Scenes - The Flash, Arrow, Supergirl, DC's Legends (HD)