"It's been kind of nice because every year I'm never involved, and I've always felt a bit left out because it's always such a huge thing and a big deal and kind of very special because obviously so much of everything leads up to it," McGrath told TV Guide. "And to be involved in it this year I was like, 'Oh, I kind of feel like part of the gang.' I felt very flattered actually... It is insane what they have managed."
In fact, it appears Lena will play a critical role in the events of "Crisis on Infinite Earths." According to the episode description for "Part One," J'onn J'onzz and Alex Danvers will go to Lena for help in an effort to save the people of their Earth:
The Monitor (guest star LaMonica Garrett) sends Harbinger (guest star Audrey Marie Anderson) to gather the worlds' greatest heroes - Supergirl (Melissa Benoist), The Flash (guest star Grant Gustin), Green Arrow (guest star Stephen Amell), Batwoman (guest star Ruby Rose), White Canary (guest star Caity Lotz), The Atom (guest star Brandon Routh) and Superman (guest star Tyler Hoechlin) - in preparation for the impending Crisis. With their worlds in imminent danger, the superheroes suit up for battle while J'onn (David Harewood) and Alex (Chyler Leigh) recruit Lena (Katie McGrath) to help them find a way to save the people of Earth-38.
"Crisis on Infinite Earths" begins Sunday, Dec. 8 at 8 p.m. ET/PT on Supergirl, then continues in Batwoman on Monday, Dec. 9 at 8 p.m. ET/PT and in The Flash on Tuesday, Dec. 10 at 8 p.m. ET/PT. After the winter hiatus, the crossover will conclude on Tuesday, Jan. 14 in Arrow at 8 p.m. ET/PT and in DC's Legends of Tomorrow at 9 p.m. ET/PT.