She is best known for her role as Mabel "Mama" Thomas on the ABC sitcom What's Happening!! from its premiere in 1976 until the end of its second season in 1978.
King's next most remembered role is that of Evillene the Witch, a role she originated in the stage musical The Wiz and reprised in Sidney Lumet's 1978 film adaptation.
She recorded on the Rama Records and Amy Records labels.