When heroes alone are not enough … the world needs legends. Having seen the future, one he will desperately try to prevent from happening, time-traveling rogue Rip Hunter is tasked with assembling a disparate group of both heroes and villains to confront an unstoppable threat — one in which not only is the planet at stake, but all of time itself. Can this ragtag team defeat an immortal threat unlike anything they have ever known?

The DC superhero universe is set to go through a major expansion this season with CBS' Supergirl and The CW's Legends of Tomorrow joining already-established CW shows Arrow and Flash, and Fox's Gotham.

While Fox's Batman prequel has thus far remained an island of sorts, the other three dramas all hail from the same producers — Greg Berlanti and Andrew Kreisberg, among others, with the hint of cross-network connectivity all but a given (despite CBS boss Nina Tassler's remarks).

"The highest priority right now is getting the new show[s] launched, and making sure the quality of the old shows stays where it is," Kreisberg told The Hollywood Reporter at TCA.

With so many shows under his producing umbrella, he — and The Flash guest star/Legends of Tomorrow star Dominic Purcell — shared a few teases of what's to come.

1. The Flash is prepping for another flashback hour.

"We're working on episode four, which is exciting, [and] there is a flashback to the night of the particle accelerator explosion, from somebody else's perspective which we haven't seen before. It's a good one," Kreisberg said.

2. The Constantine hour of Arrow is "unbelievable."

With former Constantine star Matt Ryan set to reprise his role of John Constantine on The CW series, Kreisberg praised the quasi-crossover episode. "I just read the script for five and it's unbelievable," he previewed. "You're going to be blown away." The episode will feature a resurrection, CW president Mark Pedowitz revealed to reporters at TCA, which is likely tied to the Lazarus Pit storyline.

3. The producers are already sensing the importance of Supergirl.

The upcoming Melissa Benoist-led drama marks the first DC Comics superhero show in years to be led by a woman (while ABC's Marvel-produced entry Agent Carter is fronted by Hayley Atwell).

"The most gratifying thing for me is we talk to family friends' daughters who are so beyond excited for this show, in a way you normally see boys excited for Star Wars and Batman," Kreisberg said. "I've seen young girls so excited for this. They've never really had anything like this going back from when they did Wonder Woman … That's really gratifying. For all of the talk about girl power and our goals, children are going to get that glimpse of something they haven't had before."

4. Arrow and The Flash will play host to Legends storylines as the spinoff waits for its midseason launch.

To prep for the characters in Legends to get to their starting point for the show, Arrow and The Flash will showcase a few of the prequel journeys.

"Both Arrow and Flash are helping to set those things up, in both big ways and small ways, which is lovely," Kreisberg said. "The mystery of what happened with Palmer (Brandon Routh) is playing out on Arrow. Sara Lance (Caity Lotz) will also be playing out in the first seven episodes. The Flash, we obviously have Firestorm and Martin Stein (Victor Garber) and Ronnie Raymond (Robbie Amell). And Kendra Saunders (Ciara Renee) lives in Central City in the Flash finale. Getting to know her. There's going to be a lot happening leading up to the crossover, which is serving as a [quasi] pilot for Legends."

5. The Flash will bring back Purcell's Heat Wave ... with a twist.

"Wentworth Miller (Captain Cold) and I did a scene a couple of weeks back [on The Flash]," Purcell teased. "But it was part of The Flash's dream sequence. [And] I know they're developing Captain Cold's relationship with Captain Cold's sister [there]. I think they're going to flesh Heat Wave out in Legends."

6. Supergirl addresses the Superman issue fairly early on.

Although the Supergirl pilot references Kara's famous cousin quite a bit, the show never mentions him by his name or alter ego (Clark Kent/Superman) ... but that was because of editing.

"I think the couple of times it was said, it was cut," Kreisberg shared. "it's not like Simpsons where Bart can have one 'damn' per episode."

As it turns out, the biggest use of the name came in a scene featuring a former Superman, Dean Cain. (Cain is guesting on Supergirl in a key, secret role.)

"There was originally a flashback sequence [with] Dean Cain and [former movie Supergirl] Helen Slater, and a much longer scene where he's talking about Superman," Kreisberg said. "It's one of my favorite moments of shooting the pilot was seeing Dean Cain talk about Superman. It just kept making me gush. But with the third episode coming out, it's very much about Superman's place in the world, and Kara's place in the world, and why isn't Superman going to be on our show every week. That episode has a lot of discussion about him."

7. The notion of Arrow/Flash/Supergirl promotional crossovers was news to the creative teams.

Although the brakes are being pumped on Supergirl officially crossing over with Arrow and The Flash, CBS boss Nina Tassler told reporters that the shows would be crossing over on a promotional level.

"That was sort of news to me," Kreisberg admitted. "We're obviously very excited and gratified by that. How they're going to do that, we'll see, too. They are on different networks, they are separated, but the stories Greg and I like to tell, there's obviously a symmetry. Hopefully if you're a fan of Flash and Arrow, you'll be a fan of Supergirl, and if you like Supergirl, you'll check out Flash and Arrow."

The Flash premieres Oct. 6 at 8 p.m. and Arrow bows Oct. 7 at 8 p.m., both on The CW. Supergirl premieres Monday, Oct. 26 at 8:30 p.m. on CBS. Legends of Tomorrow premieres midseason on The CW. What are you looking forward to seeing?