'The Flash' Previews "Elseworlds" Part 1 in New Behind-the-Scenes Video

The CW has released a new behind-the-scenes featurette for "Elseworlds", ahead of tonight's premiere.

The video highlights what to expect in the event's first chapter, which will come during an episode of The Flash.

"Destiny's are being altered. Realities are being flip-flopped." The Flash star Grant Gustin explains in the video. "This is the most iconic crossover we've done."

The event will see Gustin's Barry Allen and Stephen Amell's Oliver Queen in a unique circumstance, as their identities have been swapped thanks to a manipulation in reality. As fans have already seen in the promos for the event, that will come about in some very interesting ways.

"We start with Oliver waking up, and it's actually a pretty precarious situation. He wakes up in Barry and Iris' bed." The Flash showrunner Todd Helbing elaborates. "[Iris] gives him a kiss, and he's kinda like 'Woah, woah, woah. Pump the brakes.' Meanwhile, Barry, Grant Gustin, is getting his ass handed to him by Diggle. Oliver speeds to STAR Labs, to get the team to help them out. They find out that none of them know what's going on or believe them. So yeah, so they go over to Earth-38 for Kara's help. Clark Kent happens to be there, and of course, Lois Lane."

With such an off-the-wall concept, it sounds like fans can expect to see a new side of the Arrowverse's heroes, as well as the actors who bring them to life.

"Getting Stephen Amell to do comedy, he's going to surprise a lot of people." Helbing reveals. "He really nailed it. And Grant doing really dark, angry drama, he's fantastic as well. And then Melissa is always just a joy to be around. The whole cast, I think, had a blast, and it certainly showed onscreen."

"My initial reaction in reading the scripts this year was that it would be a hoot to film." Benoist explained in a previous interview. "The comedy just lives in this. Even just seeing them in each other's suits is funny; they're literally putting themselves in each other's shoes! ...[Kara] inevitably becomes kind of a middleman because ultimately there's conflict between the two and they start butting heads."

What do you think of the newest look at "Elseworlds"? Share your thoughts with us in the comments below.

"Elseworlds" will begin with The Flash tonight, December 9th, at 8/7c, followed by Arrow on December 10th at 8/7c, and Supergirl on December 11th at 8/7c.