The Flash/Arrow Crossover Spoiler: Episode To Feature A Familiar DC Villain

Minor spoilers ahead for The Flash and Arrow. Only read on if you really want to know.

Coming just before the series' midseason crossover event (and then finales) this year, an episode of The Flash will center around William Tockman, The Clock King, who previously appeared in the Season Two Arrow episode "Time of Death," TVLine reports.

Robert Knepper will reprise the role in Episode 7 of The Flash, making him the first villain to show up in both Starling and Central City. It might also explain, since they painted him on Arrow as a foil for Felicity, why the Arrow cast is drawn to the fight the following week when the eighth episodes of The Flash and Arrow cross over officially.

"We wanted to give Barry a real challenge… TWO bad guys!" said executive producer Andrew Kreisberg, adding that The Flash will be "fighting both a new enemy and one of our scariest and most successful Arrow villains in The Clock King."