The CW's "Crisis on Infinite Earths" was a rare and ambitious event in television that brought together five ongoing series while acknowledging past ones. The event's showrunner explained how the timing of the crossover's origins made the event a true rarity in television.
"It was during the story breaking on 'Elseworlds,'" Marc Guggenheim told Fake Nerd Podcast. "Greg [Berlanti] basically came into the room, and it's all of us -- all the showrunners -- in our meeting to discuss what 'Elseworlds' was going to be. He said, basically, 'It's come down from on high that we can do Crisis on Infinite Earths' -- at that point, he said -- 'next year.'"
"It was great!" Guggenheim added. "We were all blown away. We never expected that. It allowed us to do something really special, which was to use one crossover to set up the next crossover and be able to have all the shows sort of tease it over the course of a season."
"Elseworlds" was last season's Arrowverse event, and helped lay the groundwork for the franchise's current season, including the introduction of Batwoman. The Flash and other Arrowverse shows, in turn, paved the way for this season's "Crisis" event.
"It's very rare, particularly in network television, to have much lead time on something and be able to lay that much track," Guggenheim said. "That's a really rare set of circumstances, when you can do that sort of thing."