Best friends Sean and Kunle are about to have one of those nights that college comedies are built around: they’re going to hit parties at all seven Greek houses on campus, a feat known as the Legendary, and they’re going to be the first Black students in the history of their school to accomplish it. There’s only one problem: who is this white girl that is passed out on the floor of their living room, and why is she there? From that premise, “Emergency” plays like a socially conscious “Superbad,” as well as a commentary on why Black characters don’t get to have their own “Superbad.” Writer K.D….