The plot of the crossover will see Benoist’s Kara Zor-El and her sister (Chyler Leigh’s Alex) traveling to the main Arrowverse dimension to join their heroic friends at the wedding of Grant Gustin’s Barry Allen and Candice Patton’s Iris West. But things will go badly when an evil cabal from the ominous Earth-X interrupt the nuptials with bullet fire and Nazi armbands.
Among this nefarious team are dark subversions of The CW’s superheroes, including an evil Supergirl played by Benoist. Speaking to CBR, Benoist revealed that this version of Kara is the worst one fans have seen yet:
“I did play two characters [in the crossover]. I did wear a very different outfit. There’s still a cape and my face is covered and she’s not so nice. It was pretty challenging. I thought it was going to be — I’ve done here and there, I’ve had moments like that on this show with Bizarro and when Martian Manhunter takes over Kara’s body, but this was entirely different. This was not even Red Kryptonite-isque. This was way worse.”
This certainly chimes with what fans saw in the ‘Crisis on Earth-X’ trailer, where it was revealed that the evil Kara has been ruling the dark dimension of Earth-X. This goes firmly against the main Kara's moral code, and it should be interesting to watch this pair of identical enemies duke it out.
Benoist also described playing the dual roles as a challenge, “especially when we do motion control shots where I have to be in the scene with myself and it’s more tedious than a traditional split screen." This involves "memorizing a whole scene, every line, every bit of dialogue" and Benoist "didn’t anticipate how hard the transition would be to go from lightness to darkness.”
However, Benoist did go on to clarify that this was a “fun challenge” for her as an actress. It must be interesting working on one of these DC TV shows, where the writers throw weird new doppelgangers and alternate Earths at you on a regular basis. Hopefully, the episode will be as fun to watch as it seemingly was to make.
The CW's ‘Crisis on Earth-X’ crossover begins with Supergirl season 3 episode 8, on November 27.