interchangeable. But producer-director R.J. Cutler went back to the source to inspire his Apple TV+ project “Billie Eilish: The World’s a Little Blurry.” The two-hour, 20-minute film, which premiered in February, tracks the teenage Eilish and her older brother Finneas as they write and record her debut album in a now-famous cramped bedroom studio. The camera follows closely as Eilish performs a string of concerts and eventually triumphs at the Grammy Awards amid all the stress and insecurities of adolescence, amplified by eruptive stardom.