Last week, just after the Arrow and The Flash crossover event, The CW released new trailers for the fall finales of each show, airing this week. Today, The CW has released extended trailers for The Flash episode Running to Stand Still, airing Tuesday, December 8, and Arrow's Dark Waters, debuting Wednesday, December 9. As you can see in this new footage, both Barry Allen (Grant Gustin) and Oliver Queen (Stephen Amell) will have their hands full when familiar villains return to their respective cities.

The Flash episode Running to Stand Still centers on Mark Mardon AKA The Weather Wizard (guest star Liam McIntyre), who returns to break Leonard Snart AKA Captain Cold (guest star Wentworth Miller) and James Jesse AKA The Trickster (guest star Mark Hamill) out of Iron Heights. Barry must stop these rogues from taking over Central City during Christmas. Meanwhile, Joe and Iris meet Wally West (Keiynan Lonsdale). This episode will mark Wally West's debut, before he returns in the back half of this season.

Keiynan Lonsdale was cast as Wally West back in August, but it was never revealed when this character would debut on The Flash. In the comics, Wally is the nephew of Iris West, played by Candice Patton in the series. He eventually turns into the character known as Kid Flash, after an accident that is reminiscent of how Barry Allen (Grant Gustin) gets his powers. We still don't know if Wally will turn into Kid Flash at any point during this season, but it's certainly possible.

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Arrow's Dark Waters centers on Star City being attacked again, causing Oliver Queen to make a bold move against HIVE. Malcolm (John Barrowman) checks in on Thea (Willa Holland) and leaves her with a warning. Things take a horrible turn when Damien Darhk (guest star Neal McDonough) retaliates in a brutal manner at Oliver's mayoral holiday party. This new trailer also teases that Darhk has kidnapped Felicity, in an episode that "will leave you breathless."

We learned in October that Neal McDonough's Damien Darhk will also cross over into The CW's The Flash and DC's Legends of Tomorrow, although it isn't known exactly when he will show up. Executive producer Marc Guggenheim also confirmed last month that Colton Haynes will make his return to Star City as Arsenal, in this season's 12th episode, which doesn't have a confirmed air date at this time. While we wait for more details about Arrow and The Flash, take a look at the extended trailers for both show's fall finale's below.

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