MacKenzie Phillips is the daughter of The Mamas & the Papas lead singer John Phillips, the stepdaughter of actress Michelle Phillips,and the half-sister of another film performer, Chynna Phillips. MacKenzie was 13 years old when she essayed her first film role as underaged cruiser Carol in American Graffiti (1973).
She then essayed a series of juvenile-delinquent TV guest spots, which ended in 1975 upon her being cast as Julie Cooper on the popular sitcom One Day at a Time. During the run of this series, MacKenzie accepted a few outside assignments, notably a cameo as Lillian Gish (whom she closely resembled) in the made-for-TV The Silent Lovers (1980). Drug problems and run-ins with the law compromised MacKenzie's ability to function on One Day at a Time, culminating in her being fired during the 1979-80 season. After going cold turkey, MacKenzie Phillips briefly returned to the series in 1981, but her previous self-destructive lifestyle had taken its toll on her physical and emotional makeup; she left One Day for good in 1983, and has worked but little since. ~ Hal Erickson, All Movie Guide. 