Wissenswertes

Felicity referred to Oliver Queen of Earth X as "Oliver in the High Castle" a reference to the television series and novel, Man in the High Castle, which also depicts a world where the Nazis won World War II similarly, the television adaptation explored alternate dimensions in its second season.

Guest Appearance: Colin Donnell reprised his role as Tommy Merlyn, appearing as the Earth-X version of Prometheus. To accommodate his schedule, he filmed his scenes for Arrow after completing a full day of filming for Chicago Med (2015).

The Earth-X version of Adolf Hitler died in 1994. As Hitler was born on April 20, 1889, he was either 104 or 105 years old at the time of his death.

This is the second part of a four-part crossover event, begun in Supergirl episode 3x8 "Crisis on Earth-X, Part 1," continued after this episode in The Flash episode 4x8 "Crisis on Earth-X, Part 3," and concluded in DCs Legends of Tomorrow episode 3x8 "Crisis on Earth-X, Part 4."

Victor Garber (Martin Stein), Franz Drameh (Jefferson Jackson) and Dominic Purcell (Mick Rory) join Stephen Amell (Oliver Queen), Grant Gustin (Barry Allen), Melissa Benoist (Kara Danvers), Carlos Valdes (Cisco Ramon), Danielle Panabaker (Caitlin Snow), Caity Lotz (Sara Lance) and Emily Bett Rickards (Felicity Smoak) in appearing across all 4 Arrowverse shows.