The conclusion of 'Elseworlds' set up ' Crisis on Infinite Earths' as the next crossover, which aired between December 2019 and January 2020. In 'Elseworlds', Arrowverse actors portray other roles and John Wesley Shipp reprises his role as Barry Allen / Flash from the 1990 series The Flash. The title of the crossover was announced at the end of September and filming began in October 2018. Throughout August and September that year, casting for the crossover-including Ruby Rose as Batwoman, Elizabeth Tulloch as Lois Lane, and the announcement that Tyler Hoechlin would return to portray Superman-was revealed. The crossover was confirmed in May 2018 at The CW's upfront presentation, where the inclusion of Batwoman and Gotham City were revealed. John Deegan over his work at Arkham Asylum. In the crossover, Green Arrow, Flash, and Supergirl are drawn to Gotham City to confront Dr. 'Elseworlds' introduces the characters Batwoman and Lois Lane, and the fictional Gotham City, to the universe. The crossover event began on December 9, 2018, with The Flash, continued on Arrow on December 10, and concluded on Supergirl on December 11. ' Elseworlds' is the fifth Arrowverse crossover event that features episodes of the television series The Flash, Arrow, and Supergirl on The CW.