Before the casting was announced, Stephen Amell teased Spectre's arrival in "Crisis on Infinite Earths" on Twitter.On Monday, the Arrow star reflected on his weekend, even as the crossover continues filming. "Trying to relax after an amazing weekend. The spectre of the crossover still looms large," he wrote. Clearly, "spectre" was a deliberate word choice, which heralded the arrival of Stephen Lobo as Detective Jim Corrigan, aka the Spectre.RELATED: Arrow: Amell Shares A Self-Censored Crisis Cast Photo

Debuting in 1940's More Fun Comics #52, the Spectre was created by Jerry Siegel and Bernard Baily. He played a key role in Marv Wolfman and George Pérez's Crisis on Infinite Earths. The Spectre ultimately convinced the surviving heroes and villains of the DC universe to work together in attempt to stop the Anti-Monitor from destroying the multiverse. He was even powerful enough to fight the Anti-Monitor himself.

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"Crisis on Infinite Earths" has a star-studded list of guest stars. Batman: The Animated Series star Kevin Conroy, Black Lightning's Cress Williams, Batman 1966 star Burt Ward, Legends of Tomorrow's Jonah Hex, The Flash triple-threat John Wesley Shipp, Birds of Prey alum Ashley Scott and Smallville's Tom Welling and Erica Durance, as well as "Elseworlds" alums Tyler Hoechlin and Elizabeth Tulloch, are among those appearing the crossover. DC's Legends of Tomorrow star Brandon Routh has been confirmed to appear as Kingdom Come Superman.

"Crisis on Infinite Earths" begins Sunday, December 8 at 8 pm ET/PT on Supergirl, then continues in Batwoman on Monday, December 8 at 8 pm ET/PT and in The Flash on Tuesday, December 10 at 8 pm ET/PT. After the winter hiatus, the crossover will conclude on Tuesday, January 14 in Arrow at 8 pm ET/PT and in DC's Legends of Tomorrow at 9 pm ET/PT.

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