I think we can all safely say Supergirl probably should have always aired on The CW but with its move from CBS next season, one big fan extravaganza will follow. Supergirl, The Flash, Arrow, and Legends of Tomorrow will join forces for a four-show DC Entertainment crossover event.

The CW's fall schedule is looking pretty fun. We've got the full rundown here, but there is a DCTV show every day except Friday. Supergirl is set to retain its Monday 8 p.m. timeslot, keeping it up against Fox's Gotham when that returns.

After the announcement Supergirl was moving networks, but before the announcement this morning, Arrow star Stephen Amell spoke of the inevitability of a crossover. "If you have four DC superhero properties on one network, that is an opportunity that might not ever exist again, and certainly hasn’t ever existed in the history of television," he said. "So I expect them to do something."

And sure enough, The CW upfronts made it official today. According to Variety:

CW president Mark Pedowitz wouldn’t divulge any details other than to promise that planning is under way. In a conference call with reporters Thursday in advance of the network’s upfront presentation, Pedowitz expressed his confidence that producers, led by uber-exec producer Greg Berlanti, will ensure that “our annual crossover event this fall (will) be the biggest one ever.”

You know what this means? We'll have a live-action "Justice League" on TV before Zack Snyder's movie debuts. Pedowitz also apparently joked about Supergirl crossing over with Jane the Virgin and star Gina Rodriguez didn't let the opportunity pass.

The Arrow writer's room is already trying to come up with a hashtag for the huge event.

Meanwhile, another report says Calista Flockhart's return to Supergirl as Cat Grant is almost set:

While he didn't commit to it, Pedowitz seemed to indicate that Flockhart will definitely appear on Supergirl, although it's possible she might not be in every episode like she was during the show's Hollywood-based first season.

There are already some rumors floating around social media that an agreement has been struck and isn't yet announced. There have been no announcements yet to indicate that any of the show's major players will be leaving or taking a reduced role as a result of the move, although those could come at the upfront presentation in New York later today.

Are you excited about the crossover? They've always been my favorite episodes of the separate shows as it is, I can't wait to see how everyone interacts with Supergirl. Until then, we'll have to settle for this promo.

Jill Pantozzi is a pop culture writer and host who reports on all things nerdy and beyond! Her blog TheNerdyBird.com was recently relaunched with Patreon support and she’s formerly Editor in Chief of The Mary Sue. She’s written for MTV, Tor, Playboy, Publishers Weekly, IGN & more. You can keep up with Jill, and her cats, on Twitter at @JillPantozzi.