Her feature-film debut was in "Divorce American Style" (1967). She soon became one of the most recognizable (if not precisely identifiable) supporting actresses in film and television. Her roles were usually sympathetic characters, though she played a variety of other character types, including earthy, vulgar and sassy, but occasionally "with a heart of gold". A year after her feature-film debut, she became a semi-regular on the comedy-variety show "Rowan & Martin's Laugh-In", but stayed for only two months. Brennan also appeared on "Barnaby Jones"; episode titled “Blood Relations” (11/28/1975).