'Supergirl' Joins 'Arrow', 'Flash', And 'Legends' In "Superhero Fight Club" Promo; Arrowverse Crossover Villain Revealed

The Arrowverse crossover has become something of an annual CW tradition, ever since Barry Allen made his first appearance on Arrow in 2013. Arrow and the the Flash reunited again when the latter got his own show in 2015, and last year the crossover expanded even further to include characters from the then-upcoming series Legends of Tomorrow. But this year's crossover event promises to be the most ambitious one yet, bringing together the stars of ArrowThe FlashLegends of Tomorrow, and — for the first time – Supergirl.

Naturally, that raises the question of what could possibly occasion such a massive gathering of superheroes. After all, it seems safe to assume we won't just be watching them commiserate over drinks. Today, the identity of the Arrowverse crossover villain has been revealed. And while there's no footage from the actual event just yet, characters from all four shows have come together for an adorable "Superhero Fight Club 2.0" trailer from The CW. Check it out, and get details on the Arrowverse crossover, below. 

DC Entertainment and The CW spilled the beans about their Arrowverse crossover villain in a statement. "This year, for our mega Arrowverse crossover, we're taking inspiration from a DC crossover from the late 1980s known as Invasion!, which featured an alien race called the Dominators, who'd previously vexed the Legion of Super-Heroes," said Marc Guggenheim, executive producer of Arrow and Legends of Tomorrow. "We're using cutting-edge prosthetics and computer effects to achieve a feature film-quality look which is faithful to Invasion! artist Todd McFarlane's interpretation of the characters."

In the comics, the Dominators are a race of technologically advanced aliens who form an alliance with several other races to invade Earth. Ostensibly, this is an attempt to eliminate the threat posed by the planet's metahumans; in reality, the Dominators are plotting to harness the "threat" and breed a metahuman army of their own. We'll have to see how closely the Arrowverse shows stick to the source material, but in broad strokes, yup, that sounds like exactly the kind of insane plot that might inspire all our favorite metahumans to band together in order to survive.

In past seasons the crossover has arrived in early December, so we can probably expect it to arrive around the same time this year. Although the Invasion! event will probably be the only four-way crossover this season, we can look forward to some smaller crossovers as well, including FlashSupergirl musical crossover to arrive in early 2017.

Oh, and while we wait for all those promised crossovers, there's this to tide you over:

Sure, it's shameless fan service, but it's really fun, incredibly charming shameless fan service. Supergirl and the Flash are just the cutest, and Arrow's flustered response to her "kryptonite arrow" comment is a thing of beauty. Felicity and Cisco also get to drop in, not to duke it out with the other heroes but in order to manage all that fancy tech. Supergirl truly speaks for all of us when she exclaims, "This is awesome!" To watch the full Superhero Fight Club 2.0 video, download the CW app.

Supergirl season 2 premieres October 10 and airs Mondays at 8 PM. The Flash season 3 premieres October 4 and airs Tuesdays at 8 PM. Arrow season 5 premieres October 5 and airs Wednesdays at 8 PM. Legends of Tomorrow season 2 premieres October 13 and airs Thursdays at 8 PM.