Viewers were introduced to Barry Allen (Grant Gustin) during Season 2 of the hit CW drama series Arrow, in a way that made the character both likeable and intriguing, and it was easy to see why he immediately got his own TV show. With that drama series debuting on October 7th, he’ll get his own backstory and mythology and villains to fight, while also playing into the bigger DC universe and, at times, characters will cross back and forth between the two shows.

While at The CW portion of the TCA Press Tour, executive producer/writer Andrew Kreisberg, who is working on both Arrow and The Flash, spoke to Collider for this exclusive interview about following a villain-of-the-week format while exploring the larger mythology and mythos, how the show will be lighter and funnier than Arrow, that they’re throwing every idea they have at this season while knowing there’s some stuff that they won’t be able to get to until a possible second season, the big two-part cross-over episode that will come in Episode 8 of both shows, just before the Episode 9 mid-season finale, what sort of discussions they have about which characters they can use in the DC universe on TV, as opposed to the films, and how cool it is to get Grant Gustin and John Wesley Shipp in the same scene. Check out what he had to say after the jump, and be aware that there are some spoilers.

Question: Are you looking to follow the same format with The Flash that you do with Arrow?

ANDREW KREISBERG: Yeah. There will always be the villain-of-the-week, but obviously there’s more going on. To add on the pilot, there’s the ongoing mystery of what happened that night, when Barry was a child, with who really killed his mother and the long-terms struggle to get his father out of prison. That hints at a larger mythology and mythos. With Arrow, there’s only so many things the villains can do. They’re either out to kill somebody for revenge, or they’re out to rob a bank. But with The Flash, because these villains have superpowers, hopefully the villain-of-the-week aspect will become stronger. Arrow has become so serialized, and I think that’s what people have come to expect from it. With The Flash, there’s still the typical ongoing mythologies, and there’s probably even more of it than there was on Arrow, initially, but the villains-of-the-week are going to have an opportunity to be even more entertaining than they are on Arrow.

Will that be the biggest difference between the shows, or are there other differences in the approach?

KREISBERG: There are a lot of similarities, obviously, but one of the biggest differences is probably the humor. It’s a lot lighter. It’s a lot funnier. That’s not to say that it’s childish. It still exists in the same world as Arrow does.

But, you’re even filming much more in the daylight.

KREISBERG: Yeah, he’s a daytime hero and he can run outside. With Arrow, it’s always a dark alley at night, or a dark warehouse. The Flash can really run through the city, and that’s certainly been more pleasant to shoot. But, a lot of the structural storytelling is similar. There’s a healthy mix of the personal stories and the crime stories.

How much do you think of the arc of the show, as a whole, and how much are you thinking about just making a really great season?

KREISBERG: That is actually very similar to Arrow, where we have a very clear sense of what this season is about and we’re throwing every idea we have right now, at this season. But then, there are things we know we would like to get to, that we know won’t fit. So, we’re conscious of those things. With Arrow, in Season 1, we laid the groundwork for Season 2. And in Season 2, we laid the groundwork for Season 3. With The Flash, we know that there are going to be opportunities in Season 1, hopefully if there is a second season, to set things up.

You had already established The Flash in Arrow, but you have to re-establish the character and his world again, with his own show. How did you balance that out?

KREISBERG: There was a lot of discussion about how much we needed to tie those two episodes into the pilot. I think that there’s enough mentioned in the pilot with, “How was your trip to Starling City?,” and things like that. Some things were shifted a little bit and some things were left out, but I think it still feels like the events of Episodes 8 and 9 of Arrow are fresh in Barry’s head, in the pilot. If you’ve never seen Arrow before, you’ll be able to enjoy the pilot. But if you enjoyed those two episodes and all the subsequent discussion about Barry on Arrow, and Danielle Panabaker and Carlos Valdes appearing, when Felicity comes to The Flash, we’ll establish that they all know each other because we’ve heard that they all know each other. You won’t feel too much like we’ve violated the audience’s trust.

You’re already crossing over both shows, with the introduction of some of The Flash characters on Season 2 of Arrow, and then the Arrow appearance on The Flash pilot, and the announcement of Felicity in Episode 4. Will you do a two-part cross-over episode, where you have to watch both Arrow and The Flash to get the complete story?

KREISBERG: When Felicity is in Episode 4 of The Flash, it will be Wentworth Miller’s first episode as Captain Cold. And then, both Episode 8 of Arrow and The Flash will be a two-part cross-over. Not to toot our own horns, but I think we’ve designed it in a way that, if you’re not watching The Flash, you can just enjoy it from the Arrow perspective, where these crazy Flash people show up for an episode, and vice versa. We don’t want to be brazen and assume that everybody is watching both shows. Hopefully, they will be. I think it’s one of those things where, if you’re not watching both shows, whichever show you’re watching, it will all make sense to you. But at the same time, if you are watching both shows, you’re really gonna get a fun, cool two-night event.

Is it crazy challenging to set that up, so that they can be watched separately?

KREISBERG: Yeah, and you’ll let us know if we pull it off. If you’re reading The Flash and you get to the last page and Batman is there, watching them cross over from book to book and seeing team-ups are some of our favorite books, and it just feels right to be doing it in the shows. The Flash did spring from Arrow and it is the same world, and Arrow appears in The Flash pilot. So, to suggest that they don’t exist would feel wrong.

Was there any hesitation in doing that so soon, or was it important to immediately establish that they’re both in the same universe?

KREISBERG: We just want to do what’s fun and what makes us excited. Because Barry Allen made such a strong impact on Arrow, there’s a lot of left-over business, especially between Barry and Felicity. So, we really wanted to deal with that, sooner rather than later. And then, when the idea for the bigger cross-over came up, it just felt like every one of these episodes is an event. That’s one of the things we learned over the course of two seasons of Arrow. There are no miss-able episodes. What can you do to make sure that everyone watches an episode? And sometimes that’s the guest star, or the big plot twist. With these first Arrow episodes, and these first Flash episodes, because of the benefit of working on both shows, there’s something amazing and something game-changing in every one of these episodes. And then, because Episode 9 will be the mid-season finale for both shows, and they’ll have their own reasons to tune in, Episode 8 felt like a great opportunity to bring the two shows together.

Because the DC television and film worlds are growing tremendously, at the same time, and are obviously leading towards a Justice League movie in the film world, is there a lot of discussion about which characters you can and can’t use?

KREISBERG: Yeah. There really aren’t that many characters that we’ve asked to use, that we haven’t gotten access to. Fortunately for us, with Arrow, we were able to bring on Deathstroke and The Huntress, and this year we have Katana. It was actually DC comics’ idea for us to use Ray Palmer/The Atom. On The Flash, with Geoff Johns, our partner, we’ve carved out this whole world of characters that we have access to. There are the big ones that fit into the Superman, Batman, Wonder Woman mythos, but since we’re not using those characters, they’re subsidiary characters don’t really feel necessary to us. We never feel like we’re confined. We’re more impressed that we get to play with as many characters as we do. By the end of this season, on both shows, we’ll have Green Arrow, Black Canary, Katana, The Atom, Firestorm and The Flash. We’ve got a pretty good chunk of the Justice League, on both shows. We never look at ourselves as limited. We just look at ourselves as blessed that we get to play with as many of these characters as we do. You always want your lead to be the coolest character on the show. If you’ve got Green Arrow and The Flash, why would you want Batman and Superman around? I think we’ve figured out how to do those characters really well. There’s something very distancing about Superman and Batman that I think works so well in the features, but that I’m not sure would necessarily lend themselves to a weekly series. We’re very happy with the characters that we have.

You have some cool characters come up this season on both The Flash and Arrow. Have you signed those actors for a certain number of episodes, or do you have to just hope that you can get them back when you want or need them?

KREISBERG: Casting on The Flash and Arrow is always very difficult because we only have so many resources. We’ve been really fortunate that the people who we have picked have come on and, first of all, really enjoyed themselves and really enjoyed playing the characters, so they’ve been willing to come back. Sometimes it’s been by hook or by crook that we’ve gotten people to come back. John Barrowman was recurring in Season 1 of Arrow, and this year, we’ve made him a regular. In Season 1, Manu Bennett was recurring and we made him a regular in Season 2. It’s hard to keep people around, but so far, we haven’t gotten jammed too badly. We’ve just gotten really lucky. Even last year, when we had this great idea for The Huntress, we called and Jessica [De Gouw] had just finished filming Dracula, so it was perfect timing.

As a fan yourself, what was it like to get Grant Gustin and John Wesley Shipp in the same scene?

KREISBERG: From the very beginning, we were like, “If we’re doing a Flash show, we have to have John Wesley Shipp.” He is The Flash to so many of us. And he couldn’t have been kinder and more gracious and more excited. He’s such a tremendously talented actor. That scene between Barry and his father in prison is one of the most affecting scenes in the pilot. That relationship, and watching that relationship grow, is great. We have a relationship coming up where it’s really an episode between Jesse L. Martin’s character, Joe, and Henry. They’re the two dads in Barry’s life. We’re thrilled that he’s a part of it, and not just in a cameo, but he’s really the biggest part of the mythos.

The Flash premieres on The CW on October 7th.