"Crisis on Infinite Earths" viewers anxious to see the various cameo appearances from DC characters didn't have to wait very long once the event began.

Part one of the Arrowverse crossover aired on Sunday's episode of Supergirl, and the introduction wasted little time delivering the promised appearances. After a short recap featuring the Arrowverse's known characters, the cameos began rolling. The first to appear is Robert Wuhl reprising his role as newspaper reporter Alexander Knox from the 1989 Batman film. The world is appropriately designated as Earth-89.

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Next up is Curran Walters and Alan Ritchson as Jason Todd/Robin and Hank Hall/Hawk, respectively, from Earth-9 -- home of DC Universe's Titans streaming series. Russell Tovey, as The Ray from Earth-X, follows. The character appeared as a member of the Freedom Fighters on last season's "Crisis on Earth-X" event.

One of the most anticipated appearances wraps up the intro, showing Burt Ward as a civilian Dick Grayson, albeit in a Robin-colored sweater, exclaiming "Holy crimson skies of death!" as crimson skies do indeed descend on, what else, Earth-66 -- home of the 1966 Batman TV series.

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The anti-matter wave that inevitably comes in the wake of the sinister looking skies appears to claim Earth-9 and Earth-X specifically, so further appearances from those characters are unlikely.

"Crisis on Infinite Earths" continues in Batwoman on Monday, Dec. 9, and then picks up in The Flash on Tuesday, Dec. 10. After a winter hiatus, the crossover concludes on Tuesday, Jan. 14 on both Arrow and DC's Legends of Tomorrow.