Crisis on Infinite Earths

"Crisis on Infinite Earths" is the sixth annual Arrowverse crossover event featuring episodes of the television series Supergirl, Batwoman, The Flash, Arrow, and Legends of Tomorrow on The CW. The Supergirl, Batwoman, and The Flash episodes aired in December 2019 while the Arrow and Legends of Tomorrow episodes aired in January 2020. The events of the Black Lightning episode, "The Book of Resistance: Chapter Four: Earth Crisis" (which aired between Batwoman and The Flash), and a two-issue comic book with characters and concepts unused in the live-action episodes also tied into the event.