The Flash boss explains how the first Arrowverse crossover inspired season 8's 'Armageddon' event

The Flash showrunner Eric Wallace wants fans to know one thing going into "Armageddon": "This is not a crossover," he says — at least not according to the model established by the Arrowverse's most recent ones.

Sure, the five-part event kicking off season 8 features heroes from other shows, like Batwoman (Javicia Leslie) and Legends of Tomorrow's Atom (Brandon Routh), literally crossing over to The Flash, but the saga wasn't produced like "Crisis on Infinite Earths," "Elseworlds," or "Invasion." Not only that, but it's not even aiming for the scale of those multi-show epics because it just can't in the current state of affairs.

"The making of this was completely different from any other crossover we've had to do." Wallace tells EW. "That's why it's not a crossover — because we can't have 20 people in the same room all in costume fighting and giving their dialogue. It's not safe." He continues "You may not ever in this whole [story] see a scene with all the heroes at once all together as the Justice League. That's not what this story is because COVID protocols will not allow us to do that type of thing."

That being said, Wallace doesn't think fans will be disappointed by what "Armageddon" actually is because "everybody has an integral role and they're there for a reason."

Picking up six months after the conclusion of season 7, "Armageddon" follows Barry (Grant Gustin), Iris (Candice Patton), and the rest of Team Flash as they face off against the powerful alien Despero (Tony Curran). The threat Despero poses is so big that the team ends up recruiting several familiar Arrowverse faces to help them, including Black Lightning (Cress Williams), Supergirl's Sentinel (Chyler Leigh), Arrow's Mia Queen (Katherine McNamara), and "Crisis on Infinite Earths" newcomer Ryan Choi (Osric Chau), as well as from the aforementioned Batwoman and Atom.

While it was the CW's idea to start season 8 with a guest star-filled adventure, Wallace conceived the "Armageddon" storyline four years earlier while working on "Crisis on Earth-X," the 2017 crossover about super-Nazis from parallel world invading our Earth.

"There's a specific scene in 'Crisis on Earth-X' that I remember when we were writing it, I thought, 'Well that's interesting. What if we spun off of that?' And that's how we got this story," says Wallace, declining to reveal the specific scene out of fear of spoiling "Armageddon." "When the CW asked what I could come up with, I pulled [this idea] back out. It was originally going to be with a very different villain. It wasn't Despero, but I won't tell you who it is because I'm trying to bring that villain onto the show."

Dusting off that years-old idea was the easy part. From there, the writers had to figure out how to tell a large scale story while also adhering to COVID-19 safety protocols, which place a number of restrictions on shows including the number of people who can be on set and in a scene at any given time. Thankfully, two pieces of pop culture held the answer. The first was Matt Reeves' 2008 horror movie Cloverfield.

"They did such a great job in Cloverfield of telling this story about a huge monster tearing New York apart but you never really see the monster. It's not about the monster. It's about the people on the ground and what they're going through. It's a very, very emotional movie," says Wallace. "I realized that was the key to how we need to tell the 'Armageddon' story, which then led me to the following simple edict that went through all of production: This is Barry's worst day ever. So you have smaller scenes, but there's an epic thing and epic scale and epic jeopardy that are kind of going on in the background or implied... It's big but that bigness isn't always where the camera is focused on. The camera is focused on Barry, or Barry and Iris, or the Flash plus 'insert guest star here.'"

The writers were also inspired by "Flash vs. Arrow." The first part of the Arrowverse's inaugural crossover between The Flash and Arrow, that season 1 episode helped them understand how to integrate all of the heroes into the story. As they started breaking "Armageddon," Wallace and the team realized they couldn't and shouldn't even try to reach the heights of "Crisis on Infinite Earths," so they decided to do the opposite and tried to craft a tale with the intimacy of Flash and Green Arrow's (Stephen Amell) very first team-up.

"[Flash vs. Arrow was] just two dudes. It's Flash plus blank, and that became the new template. It might be five episodes, but every adventure that happens along the journey to stop Armageddon should be 'Flash plus blank,'" says Wallace. "In 'Flash vs. Arrow,' you have whole scenes of Barry and Oliver [getting] to spend time together not in costume, just communicating, talking, getting their emotions out, having a beer together — things that you never have time for in a crossover, except for at the very end in the coda."

With all of that taken into account, "Armageddon" isn't "the biggest most spectacular crossover because we can't outdo 'Crisis on Infinite Earths,' but I think it is by far the most emotional one by far," says Wallace.

When it came to deciding which heroes to insert into the story, Wallace focused on ones who could best support Barry's "special" emotional journey over the course of the five episodes. Batwoman and Black Lightning were the first two characters Wallace thought of, followed by McNamara's Green Arrow, who was last seen in Arrow's series finale. (Here's more information on Batwoman's role in the story.)

"As we started to break it, it became obvious that Mia Queen had to be in the ending chapters of this," says Wallace, who recommends fans rewatch Arrow's penultimate episode "Green Arrow and the Canaries" before the premiere. "She has to be in this story because of what is being told. It's all intertwined. There's some really great Iris stuff with Mia Queen that I'm very excited about people to see that really was integral to the overall story."

For Wallace, it was important that these guest appearances weren't just cameos. "Every single guest star has their emotional journey that they go on. There might be one exception, but it's a pretty darn funny storyline. There's some real humor there," says Wallace. "That's different because in a traditional crossover we'd never have the time to service all of the characters and honor them. I realized we can't do that. We have to go back. And that means less characters, but more screen time."

According to Wallace, the visiting actors appreciated this approach. "When [McNamara] first read the script, she said [to me], 'Oh my gosh, Eric, thank you so much. You're not just honoring what came before with my character's journey. You've expanded on it and done all the things that I hoped we would be able to do and hint at.' I said, 'That's because we're not just trying to open the door to our guest-star and characters and say, here you are. We're trying to kick the door down permanently and say, 'You're a part of this world now and you can come and go at any time,'" says Wallace. "That's one of the endgames of 'Armageddon' that I don't think people will really get at first. But when you see how everybody fits into this, yeah Mia can show up in the very next episode. She doesn't, obviously, because we only have her for 'Armageddon.' But now it's much more of an interconnected universe because the character relationships, we made sure they're much more intimate."

All of that being said, "Armageddon" definitely isn't just about hanging out at the Hall of Justice. At the end of the day, it's a Flash story and the first three episodes launch each character's storyline for the year, especially "Armageddon, Part 1."

"This is a season premiere of The Flash," says Wallace. "['Part 1'] was the hardest episode of The Flash I ever had to write, because it had to do so much that was not anticipated. But I loved it. I hope everybody enjoys the results because I think there's some really wonderful surprises and also a lot of humor in 'Part 1' that I wasn't expecting. I think 'Part 1' got funnier when I realized I had to honor not just kicking off a season but kicking off a crazy space story."

"Armageddon" also has an effect on season 8 as whole because it forced Wallace to slightly alter the multi-season plan he's had since he took over as showrunner in 2019.

"I'm happy to report that we were able to work it [into the plan] and setup what is the final graphic novel of season 8 in the exact way," he says. "We're going to get to the same place at the end of season 8 that was part of the original three year plan. We're still going to get there, but it's almost like we have this great kind of setup that kind of puts everything into motion."

The Flash returns Tuesday at 8 p.m. on the CW.

Related content:

• The Flash star Grant Gustin warns Batwoman team-up isn't 'what everybody would expect'
• The Flash star Grant Gustin teases Barry and Black Lightning's 'heavy' reunion in 'Armageddon'
• The Flash faces down Despero in 'Armageddon' crossover first-look photos