Normally these "inside" videos from the CW looks at specific episodes and the executive producer(s) talk about what is involved, this one for Supergirl does include EPs Jessica Queller and Robert Rovner as most do… but then it moves passed them to look into some of the behind-the-scenes filming for the Crisis on Earth-X crossover. The opening to the event showed each main hero in their city dealing with something. Where Flash (Grant Gustin) is fighting King Shark, Green Arrow (Stephen Amell) and White Canary (Caity Lotz) and her team are fighting tax collectors or something… Supergirl (Melissa Benoist) has to take on a Dominator. The Dominators were the aliens featured in last seasons Invasion crossover and Kara even calls them out as, "so last year". It's a funny moment and we ignore the questions of how did a Dominator get to Earth-38, etc.
From there it shifts to the big action scene in the episode, the fight at the church. Here we get to see some of the green screen and wire work they did to film the episode, but also a lot of the practical stunts done with Lotz and Chyler Leigh as they work together to take on some Nazi soldiers and eventually the Earth-X version of Prometheus. You get the impression from this footage that Lotz can kick some serious butt in real life.
Supergirl airs Mondays at 8 PM on the CW.