Who else is returning for the landmark hour?

By Natalie Abrams
October 18, 2016 at 08:16 PM EDT
Diyah Pera/The CW (both)

How will Kara Danvers make her way to the Arrowverse for the upcoming four-way crossover between Arrow, The Flash, DC’s Legends of Tomorrow, and Supergirl?

“Last year, Supergirl established that Flash was able to make his way to what I call Earth-CBS, and it stands to reason that, with the proper breach technology, the reverse can happen,” executive producer Marc Guggenheim told reporters Tuesday following a screening of this week’s Arrow and Legends of Tomorrow.

In the crossover, the heroes will team up to fight against the Dominators, who in the comics were a technologically advanced alien race that wanted to invade Earth and eliminate the threat posed by unpredictable metahumans — and they have similar motivations during the crossover. “Once the heroes realize that they’re up against aliens, they decide that they need an alien on their side,” Guggenheim says. “Fortunately, Barry knows a really nice one. I don’t think it’s a big shock that between Barry and Cisco, and all their experiences with Earth-2 and the multi-verse, that they can pluck her from Earth-CBS.”

Guggenheim also revealed that the crossover will actually kick off at the end of an episode of Supergirl, where Cisco (Carlos Valdes) and Barry (Grant Gustin) basically enlist Kara’s help. “Some people call it a four-way crossover because it involves four shows; my ulcer requires me to call it a three-part crossover,” Guggenheim explains. “The story that’s being told has a beginning, middle, and end: a beginning in Flash, a middle in Arrow, and an end in Legends. But Supergirl is very much a part of the whole thing, so we are crossing over four shows — four shows in three parts.”

The biggest challenge the producers faced in creating the crossover was not actually bringing all these heroes together, but also telling the story within Arrow‘s upcoming 100th episode. “When the news broke that the 100th episode was also going to be the crossover episode, people were up and down my Twitter and Greg [Berlanti’s] Twitter I think, in this case, in a very positive way,” Guggenheim says. “People didn’t want to feel like the crossover was highjacking what should be a really seminal episode and a seminal moment for the show Arrow, which I think is wonderful. Greg came up with an idea that really does allow us to have our cake and eat it, too.”

In addition to original cast members Jamey Sheridan, Katie Cassidy, and Susanna Thompson returning, Guggenheim revealed that John Barrowman and Neal McDonough will both reprise their roles as Malcolm Merlyn and Damien Darhk, respectively, in the 100th episode. “I haven’t seen the episode all cut together yet, but it has some incredibly iconic moments,” he says. “It is a love letter to the show, it draws on all previous 99 episodes pretty much. Everyone who we could have in the episode, from a scheduling point of view, is in the episode. Even the people who we couldn’t have, because of conflicting schedules, are represented. At the same time, you’ve got Flash and Supergirl; that’s an enormous amount of fun. Certainly the recruits also play a very large role, an important role, in the episode. I’m really excited about it.” By recruits, Guggenheim is referring to the new Team Arrow, which includes Curtis (Echo Kellum), Wild Dog (Rick Gonzalez), Ragman (Joe DiNicol), and Evelyn Sharp (Madison McLaughlin).

With that said, Guggenheim had high praise for Stephen Amell’s performance in the landmark hour. “There’s one moment in it that I think is probably Stephen’s finest performance to date,” he says. “This one scene, that really has two moments within the one scene, it will break your heart. It will take your heart, pull it out, and stomp it on the floor. It’s very, very affecting. It’s all on Stephen’s back. It’s incredible. Willa [Holland]’s amazing in the episode. Everyone obviously brought their A game to it. I’m really, really excited about it. It’s the 100th episode!”

The Flash-Arrow-Supergirl-Legends of Tomorrow crossover is expected to kick off in November. Just before it, all four CW superhero shows will be represented at EW PopFest. Click the banner above for details and tickets.