Ethan Shanfeld “Brat” summer might be over, but nothing is truly dead until “Saturday Night Live” gets its hands on it. On Saturday’s season opener of the NBC sketch comedy series, Bowen Yang transformed into Charli XCX to host a fictional series called “The Talk Talk Show,” in a nod to one of the British pop star’s song titles. In the segment, Yang welcomed “Australian dingo twink Troye Sivan,” with whom Charli XCX is currently on the Sweat Tour.