Tonight The CW aired the first official promo for the highly anticipated 4-night crossover event for "Supergirl," "The Flash," "Legends of Tomorrow," and "Arrow." The promo featured Barry Allen introducing Supergirl to the teams and boasted the event tagline "Heroes vs. Aliens."

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The 4-night crossover will pit the DC superheroes against a force of aliens called the Dominators. The Dominators will exercise mind-control powers over the team of heroes, which means the heroes will likely fight each other at some point. The "Heroes vs. Aliens" event will begin on "Supergirl" on November 28 and will conclude on "DC's Legends of Tomorrow" on December 1.

Starring Melissa Benoist as the Girl of Steel, “Supergirl” airs Mondays at 8 pm ET/PT on The CW. The network is also home to Grant Gustin as the Scarlet Speedster in “The Flash,” airing Tuesdays at 8 pm ET/PT, Stephen Amell as the Emerald Archer in “Arrow,” airing Wednesdays at 8 pm ET/PT and Arthur Darvill, Brandon Routh and Caity Lotz in “DC’s Legends of Tomorrow,” airing Thursdays at 8 pm ET/PT.