It's crossover time over on The CW, and that means it's time for Arrow's 100th episode.

The Arrowverse will stage an unprecedented four-show crossover event this fall, brining together Greg Berlanti's Supergirl, Flash, Arrow, and Legends of Tomorrow. Filming for the extravaganza will begin later this week, and executive producer Marc Guggenheim posted a little teaser on Monday.

Although you can see the title, the script page reveals the director (James Bamford) while the Arrow writers room disclosed the air date (Nov. 30). Bamford is the stunt coordinator for the series, and, with Oliver's gritty season 5 fighting style, the episode 8 director certainly has his work cut out for him.

So who can you expect to see in the milestone episode? Well, it looks like the good folks of National City will be the ones to hit the road, making pit stops in Central City, National City, and wherever in time Rip Hunter's crew is chilling.

"It's an external threat from outside the shows that will involve Supergirl coming over to The Flash, then Arrow then Legends of Tomorrow," Guggenheim told Cinema Blend.

Considering Diggle's awed reaction to meeting the Scarlet Speedster, you can bet the arrival of a bona fide alien will leave him floored.

Find out more when Arrow returns to The CW on Oct. 5 at 8 p.m. ET. Click the video below to see the latest trailer for the season premiere, which is titled "Legacy."

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Tags: Arrow television the cw