Andrew Kreisberg is one of the few people with real power to control both Supergirl and The Flash – that’s because he executive produces both superheroes’ TV series on The CW, charts their respective destinies, and occasionally brings them together in the fight for justice.

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During The CW’s press day for the Television Critics Association, Kreisberg was on hand to join a handful of reporters for a quick, rapid-fire Q&A session addressing a hodgepodge of inquiries related to both shows, and in several cases provided some eye-opening responses.

On the upcoming “The Flash”/”Supergirl” musical crossover:

Andrew Kreisberg: Hearing Melissa [Benoist] and Grant [Gustin] sing -- it’s funny. You guys only ever see the episode. To me it’s like, I think about every episode, it’s also the experience of making it. I can’t tell you how many times I’ve been on set with Melissa, or when Melissa and Grant were there. They were just singing between takes. So it’s like, I hear Melissa sing all the time. So for you guys to get to hear that finally will be so great.

What I love about it, and it’s what I always loved about what Joss Whedon would do like with “Hush,” or “The Body,” he’d have these very special episodes, but they were intrinsic to the storytelling, the ongoing storytelling that was going on. So when we get to the musical episode, both Barry and Kara will find themselves at pivotal crossroads on their respective series, and the experience of going through the musical will have a great impact on both series moving forward.

There are going to be people from both shows singing. It’s going to start on “Supergirl,” and it’s going to resolve on “Flash.”

We’ve had singing on “Flash” before. We had Barry sing karaoke. We had Jesse sing in the alternate universe. But to be able to have a full-fledged musical episode, as much as we hope these shows speak to people, whether socially, or Alex’s storyline and what it means to people, at the end of the day, we’re trying to entertain people. We feel like no one is trying harder to just flat-out entertain people than this quartet of shows. So to be able to do a musical episode is so exciting.

On the prospect of bringing Neil Patrick Harris, the voice of the animated villain the Music Meister, in to play the live-action version:

We’re certainly huge fans of his. As the casting process proceeds, we’ll see what happens.

On whether the songs featured will be original works, covers or a mix of both:

We’re still working that out right now. We’re still writing the script and trying to figure out exactly what we’re going to do.

On finding story paths and consistent tones that differ from the DC films in production and development that often feature overlapping characters while still not limiting things to “ligher” interpretations:

I don’t really know what the future holds for DC movies. I only know what’s happened. Whether it was a DC movie, or a “Star Wars” movie, or a Marvel movie, we try to avoid things that are sort of already out there.

I think that we have such an amazing cast on “Supergirl.” They can handle just about anything. I think that the darker tones sometimes work a lot better once you’ve got a few years under your belt, where you really do care about these people. So that when things take a bit of a darker twist, it feels a little bit more earned and it doesn’t just feel like, “Now it’s time to torture your characters.” So I think the tone of “Supergirl” will stay consistent throughout the season. So we’ll see what happens in the future.

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On what’s ahead on the villain front for Supergirl:

She’s still facing Cadmus. There’s going to be a couple of other returning villains. Livewire is coming back and Parasite’s coming back. She’s going to face off against Mr. Mxyzptlk, so we’ve got a bunch of classic DC comics characters.

I think a lot of the pull of the next episodes is the mystery of Mon-El, and what is he hiding? And who are these people who are tracking him? That coincides with the two of them growing closer and seeing where that relationship goes.

On the real-world response to Alex’s coming out story:

I’ve seen [Twitter threads] of people saying that watching the show, they were able to start the conversation with their own families. It’s beyond humbling and beyond gratifying to know that this show has the ability, not only to entertain, but to really create a safe haven in opening discussions with people. What could possibly be more important?

On how Barry and Iris will begin to address the prospect of Iris’ predicted future death:

I think ultimately, whether they do get out of it is sort of the question. What’s interesting is, in an upcoming episode, they learn a little bit more about the future, and they now have a list of things they know will occur between now and May.

Their operating principal is: can they stop enough of these things to sort of change time? So they have a little bit of a road map. It’s fun for us because it reminds me of Oliver’s list. They’ve got like a mission for weeks to see if they can change the future, which is something we’ve never explored before.

Most of “Flash” has been about the hold that the past has on you, and how you can’t change your past, and you can’t change the terrible things that have happened to you. They’ve never really had to deal with knowing something terrible is coming down the pike, and can they avert it? Do the decisions that they make bring them closer to the inevitable event? Or are they going to be able to think their way around it?

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On whether the Black Flash will turn up in the current season of “The Flash”:

Yes, he will. I will say that you might be seeing him on multiple shows. The classic comic book Grim Reaper aspect… He’s a classic character. We have storylines on multiple shows that fit having him turn up.

There’s something so scary about him, even scarier than when he was just a man, because now it’s like he's the Grim Reaper. He is like the Devil, and how do you stop the Devil? So it presents an interesting challenge for the heroes of the respective shows in which he appears.

On the behind the scenes logic that let actor John Wesley Shipp transform from Henry Allen to Jay Garrick:

It’s funny because when John was original cast in the pilot, we didn’t reveal his role, and so many people thought he was Jay Garrick and thought that was so perfect. For us, we just felt like it was sort of like a cross-timing, where at the same time we felt like, “What was Henry bringing to the table?” Because once he was out of prison, it just felt like we weren’t sure how much real estate we wanted to provide to that relationship.

At the same time, we had this mystery of this man in the mask, and it just seemed so delicious, the idea that Barry’s father would pass away, and then he would have this new person in his life who was wearing his father’s face. I think what made having Jay on the show so special is, it’s not so much the history of Jay Garrick, but that this hero, this other Flash who Barry has to work with, has the face of his deceased father, and the emotion that goes along with that.

[John’s past history playing The Flash is] the meta level on which this show works a lot of times, which for us, to be able to get John Wesley Shipp back in a Flash suit and have that scene with him and the Trickster with Mark Hamill was just, even though it was a brief little snippet, it felt like the old “Flash” show for a second, and that made us so happy.