Back in early December, The CW aired an epic four-night crossover that featured all of their DC Comics heroes coming together, Arrow, The Flash, Legends of Tomorrow and the network's most recent addition, Supergirl. Since Supergirl was moved from CBS to The CW for its second season, Kara Zor-El didn't fit into this crossover story too much, with only a brief epilogue at the end of the episode setting up the rest of the crossover. Next season, however, producer Andrew Kreisberg revealed that they have listened to fans' complaints, and they will put together a true four-night crossover event.

The four-night crossover featured these DC heroes squaring off against an alien race known as The Dominators. Some fans complained that Supergirl wasn't a big enough part of the crossover, and when Entertainment Weekly caught up with executive producer Andrew Kreisberg, who works on all four shows, he revealed that they plan on addressing the fans' concerns by crafting a true four-night crossover that features all of these heroes equally. Here's what the executive producer had to say about next season's crossover below, and why Supergirl wasn't as big a part of this season's crossover.

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"Next year, we're hoping to do a true four-way crossover. The great thing about our dear friends at the CW and Mark Pedowitz picking the shows up as early as they did has allowed us to start building the schedules for next season. One of the big things we learned from two years ago, which made the crossovers this year slightly easier, was building in shut-down days, where shows just went dark. The single hardest factor in doing the crossovers is actors' availability because the shows keep going on. You're basically juggling four shows worth of schedules. The thing that we didn't really plan on, because we weren't aware that we were going to switch Supergirl from CBS to CW and it was really going to be part of it, that was the one show that didn't have built-in shut-down days, so all the other ones did. Melissa Benoist ended up being heavily in Flash and then in Arrow, so Supergirl was the one we needed to shut down the most and it was the one that we didn't have any opportunity to. Now that we've gotten the early pickup and we've started designing the seasons, we're building in those dark days, and actually more dark days on Supergirl than the other shows, to make it a little easier."

While fans will have to wait several months for that crossover to air, there is still another, smaller crossover that fans can look forward to, which will have plenty of Supergirl. The CW recently announced that their Flash and Supergirl musical crossover event will begin with the March 20 episode of Supergirl and continue with the March 21 episode of The Flash. The villain for this crossover will be the The Music Meister (Darren Criss), who, in the DC Comics, has the power to control his victims through song. That crossover will predominantly take place on The Flash, with Supergirl characters Kara, Winn (Jeremy Jordan), J'onn (David Harewood), and Mon-El (Chris Wood) crossing over to The Flash. Here's what Andrew Kreisberg had to say about how he wishes he could have brought all of the Supergirl stars on board.

"We would've had everybody, because I know this one (Chyler Leigh) can sing, but somebody actually had to be part of an episode of Supergirl, because we actually keep filming these things."

The Flash's Grant Gustin and Supergirl's Melissa Benoist, who both shared the screen on Glee before stepping into their superhero roles, previously crossed over in a Supergirl Season 1 episode where The Flash was mysteriously transported to National City. Other CW stars who will be involved in musical performances include The Flash's Jesse L. Martin and Carlos Valdes and Legends of Tomorrow stars Victor Garber and John Barrowman. With this crossover just a month away, we should have some new trailers and clips surfacing soon. As for next year's four-night extended crossover, we likely won't know anything about that event for quite some time, but there may be some hints dropped during The CW's annual presence at Comic-Con.