Supergirl star Melissa Benoist has weighed in on the "massive," "overwhelming" crossover between all four Arrowverse shows. In the upcoming event, Benoist will double up on her usual role, playing both the Girl of Steel and her evil Earth-X doppelganger. During a set visit, she discussed the gigantic scope of "Crisis on Earth-X" and teased the "fun challenge" of playing two characters in the same scene.

"I said to myself at the end of last year's crossover, 'There's no way it could get bigger than this. How are they going to write something bigger than this?' Well, they wrote something massive that was overwhelming to read, in an exciting way of course, but also at the same time like I had to brace myself," she shared. "I think we all did. Everyone goes to Central City to Iris and Barry's wedding, but of course it's the comic book world so not every wedding goes as planned. You'll have to see, it's pretty crazy. They get some really evil visitors from Earth-X."

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As to Alex Danvers' involvement in this year's crossover, Benoist said, "I always wished that she [Chyler Leigh] had been by my side for every crossover that I've done, which I guess are just the two last year. Because they are always so massive and such undertakings workload wise."

She also weighed in on her other role in the crossover: Supergirl's evil Earth-X doppelganger. "I did play two characters. I did wear a very different outfit. There's still a cape and my face is covered and she's not so nice," she teased. "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."

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Asked if it was difficult to fill this new role, she said, "Yeah, 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. And essentially, you're memorizing a whole scene, every line, every bit of dialogue and I didn't anticipate how hard the transition would be to go from lightness to darkness. A fun challenge."

This year’s four-part crossover will air across two nights, beginning Monday, Nov. 27 with Supergirl and Arrow (on a special night for one week only) and concluding Tuesday, Nov. 28 with The Flash and Legends of Tomorrow.