Arrow type TV Show network The CW genre Superhero

This Saturday at EW PopFest, four of TV’s greatest superheroes joined forces onstage — and they’re about to do it again on TV.

EW’s Natalie Abrams moderated a superpowered panel featuring Supergirl’s Melissa Benoist, Arrow’s Stephen Amell, The Flash’s Grant Gustin, Legends of Tomorrow’s Caity Lotz, and the mastermind behind them all, superproducer Greg Berlanti. The fivesome talked about their own respective shows as well as the Berlanti-verse’s upcoming four-way crossover, titled Invasion, which will see the heroes work together to take on the Dominators.

“They’re all going to have their own continuing storylines,” Berlanti assured the PopFest crowd. “It really does feel like, in the middle of the season, a three-hour movie.”

During the mega-crossover, Arrow will celebrate its landmark 100th episode, and Amell wouldn’t have it any other way. “To me, the 100th episode had to be a crossover,” he said, calling the team effort “emblematic” of what the show stands for. “It gives us a chance to do something for the fans that, in the normal course of our season, we would never get to do.”

Gustin, who has taken part in every crossover episode so far, promised that this new one will be unlike any that you’ve seen. “This one’s just bigger,” he said. “Almost everyone interacts with every other character at a certain point.”

Arrow fans also have the arrival of Dolph Lundgren to look forward to. The famed action star will soon debut as the flashback villain Kovar. “He brings a different energy to the show. The first time we meet him, it just feels different — even the way that it’s shot,” said Amell, who named Lundgren’s Universal Soldier, He-Man, and Rocky IV as three of his favorite movies growing up and could hardly contain his enthusiasm when it was pointed out that the two of them will probably get the chance to fight onscreen at some point. “I mean, come on,” he said. “Come on.”

On a more personal note for Oliver, the status of his relationship with Felicity (Emily Bett Rickards) will take center stage in the upcoming episode. “We haven’t really discussed our relationship yet this season,” Amell said, “but Oliver and Felicity discuss a little bit about the relationship, and where it is, in this week’s episode.” Berlanti added, “Obviously, they work together every week. They’re very close. I can’t imagine anyone that would ever be in either of their lives that would replace the other person.”

Gustin also teased the upcoming arrival of this season’s second big bad on The Flash: Speedster villain, Savitar, is coming “very, very soon,” Gustin promised.

“He’s the god of motion,” Berlanti added, “so Flash is up against his biggest foe yet.”

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Gustin also touched on how Barry is dealing with turning the timeline upside down with Flashpoint. “Barry’s got a lot of feelings. He’s a sensitive guy. He beats himself up, I think, quite a bit,” he said. “As soon as he starts to realize what the repercussions are, it weighs on him heavily.”

But Berlanti isn’t going to turn back. “I’m not sure that we can [return to the original timeline], given what we’ve established,” he said. “If we’re not challenging ourselves and creating new territory and new obstacles for the characters, I think it’s less rewarding to watch and probably less rewarding to play. We like to grow ourselves and grow our characters.”

Lotz’s Sara is also navigating change as the new leader of the team on Legends of Tomorrow. “I think she’s kind of naturally been backseat leader [already],” the actress said. “But now that it’s actually her responsibility, I think it’s kind of stressful, because everything’s your fault. She’s kind of got to get her act together.”

Ultimately, the question came up over which superhero would win in a showdown between them, and a debate sparked among the actors. Benoist, naturally, thought Supergirl would reign supreme. “She’s got heat vision! She flies!” she argued. Amell wasn’t having it. “I’ll let you destroy each other and then I’ll come in and mop up,” he said.

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It was Berlanti who finally put an end to the argument: “You’ll see some of that in the crossover.”

Supergirl airs Mondays at 8:00 p.m. ET, The Flash airs Tuesdays at 8:00 p.m. ET, Arrow airs Wednesdays at 8:00 p.m. ET, and DC’s Legends of Tomorrow airs Thursdays at 8:00 p.m. ET, all on the CW.

Watch the full CW Superheroes panel from EW PopFest here on the PEOPLE/Entertainment Weekly Network (PEN). Go to PEOPLE.com/PEN, or download the free app on your Smart TV, mobile and web devices.