When Sara confronts the Nazi doppelganger of her father Quentin, the music playing in the background is "Eidelweiss", a song specifically written for The Sound of Music (1965) and used as a symbol of defiance against the Nazi annexation of Austria. The original symbolism of a small white flower as an expression of resistance can be extended to Sara, the White Canary. Martin Stein sang the song to Adolph Hitler in a second season episode of Legends of Tomorrow.
Hey, you're cutting it too close.
Leo Snart: I thought that was great timing. I really enjoyed the pun.
Barry Allen: So you're Leonard Snart's doppelganger.
Leo Snart: No, I'm Leonard Snart, but you can call me Leo. That is a fantastic outfit. Did you make that?
When Green Arrow, White Canary, Citizen Cold and Alex Danvers attack the Portal compound on Earth-X, while shooting, the drawstring for Oliver's bow disappears each time an arrow is fired. This is due to the CGI used.
The usual opening narration and title card are replaced by a special "Crisis on Earth-X" sequence.