The CW crossover event Crisis on Infinite Earths happens in December and January. ‘Crisis on Infinite Earths’: Showrunner Marc Guggenheim on Plotting The CW’s Six-Show Crossover Event. The event, titled "Crisis on Infinite Earths," will include characters from "Arrow," "The Flash," "Supergirl," "Legends of Tomorrow," "Batwoman," and "Black Lightning." Crisis is based on the DC comic book series. The yearly Arrowverse crossover event has become a staple of The CW, but we've never seen one as epic as Crisis on Infinite Earths.

The crossovers happen on Supergirl December 8, Batwoman December 9, The Flash December 10, and Arrow and DC’s Legends of Tomorrow January 14. The CW's Arrowverse crossover will span across four nights, beginning on Monday, December 9 and concluding on Tuesday, January 14.