"Elseworlds" is the fifth annual Arrowverse crossover event, featuring episodes of the live-action television series The Flash, Arrow, and Supergirl on The CW. The crossover began on December 9, 2018, with The Flash, continued on Arrow on December 10, and concluded on Supergirl on December 11. "Elseworlds" introduces the characters Batwoman and Lois Lane to the universe, as well as the fictional Gotham City. In the crossover, Green Arrow, Flash, and Supergirl are drawn to Gotham City to confront Dr. John Deegan over his work at Arkham Asylum.