As with the past two years, a big crossover is coming to The CW's DC Comics-based shows. But this year, there will be twice as many shows involved as before. "Legends of Tomorrow" and "Supergirl" -- which has jumped from CBS to the CW -- will join "Arrow" and "The Flash" to form a nearly weeklong event that will most likely air in late November (although the official date has not been set).

During press events for the involved shows held at Comic-Con International in San Diego, members of the "Arrow," "Flash" and "Supergirl" cast and crew looked toward the crossover. The big event will coincide with "Arrow's" 100th episode, and most likely will celebrate the massive universe -- comprising three other shared-multiverse series -- that one show has spawned.

"I can tell you it's our hundredth, which is exciting," said "Arrow" Executive Producer Wendy Mericle. "We are just sort of getting into it right now. It's going to be the biggest one we've done, it's going to involve all four shows, which is unprecedented. Every year we think, 'oh, we've figured this out, we know how to do two shows, now we're adding in three shows, and we've never had to do four. It's going to be interesting. It will be a four-part story, 'Supergirl' airing first will obviously be the kickoff​."

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And now that "Supergirl" is on the same network and filming in Vancouver, EP Sarah Schechter says joining in on the crossover fun is a lot easier. "We have a very ambitious crossover week planned for this year," said Schechter. "And certainly having them all on the same network and [filming] in the same city makes that much more achievable."

It was pointed out that while "Supergirl" has crossed over with "The Flash" before, the ex-CBS series currently exists in a different universe from the other three shows. Could the fall event do something about that, similar to the iconic seres "Crisis on Infinite Earths"? Schechter kept things vague with her answer, only confirming that there will be "big events." She added: "I look forward to all of the Reddit discussions of what they might be. But yeah, we have some really fun things planned."

If the producers know what's going on in the crossover, they aren't telling anyone -- including the actors, it seems. "Flash's" Carlos Valdes, who plays Cisco Ramon on the series, spoke to the crossover's mysterious nature. "I don't think anybody knows anything about the crossover," said Valdes. "I don't even think the writers know what's happening in the crossover. I'm sure that Cisco's storyline in the crossover is gonna be filled with humor and strange and unexpected relationships."

"I hope I'm in it, because I don't know that," said Keiynan Lonsdale with a laugh. In season three of "The Flash," Lonsdale will take on the super speedster role as the costumed Kid Flash. "I hope I'm a part of it and it would be really cool if I was a part of it in a Kid Flash way. I have no idea. I'll find out not too soon before you guys. I'm not sure if I want to ask them or just wait until scripts come."

There's one big variable with the crossovers, though: whether or not Tyler Hoechlin's newly-cast Superman will take part in any of the four chapters. The Man of Steel is set to debut early in "Supergirl's" second season, and the prospect of meeting the icon clearly excited some of "Flash's" actors.

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"I think if Cisco met Superman, that's definitely just a playground for references and it'd be a nice dynamic to explore, but we'll see," said Valdes.

"Flash" lead Grant Gustin, a big Superman fan, said he's "real excited, really really excited" to see the character join the universe. But he had disappointing news to break. "They haven't said if I'm allowed to say this or not, it's kind of a reverse scoop," said Gustin. "We're not going to get to be on camera together. I know that much. Superman and Flash won't -- I won't be in a scene with him." When asked if that includes the crossover, Gustin said, "I don't know. But the early part of the season, his first few episodes that he's doing, I won't be in a scene with him. Because they're going to be establishing the Supergirl/Superman relationship. I'm just excited that he's on the show."

The CW's superhero lineup kicks off another season when "The Flash" returns on Tuesday, October 4. The four-part crossover will air later this fall.