Biography: From Wikipedia, the free encyclopedia. April Stewart (aka Gracie Lazar) is an American voice actress. She is best known for providing the voices of several female characters on the animated cartoon TV series South Park alongside fellow voice actress Mona Marshall. Born and raised in Truckee, California, Stewart started acting at the age 12. Her father, Freddie Stewart, was a singer with the Tommy Dorsey Orchestra. In early 2008, April Stewart had her first child. April is the voice of Liane Cartman, Sharon Marsh, Mrs. McCormick, Shelley Marsh, The Mayor, Principal Victoria, Wendy Testaburger and numerous other characters starring in South Park. She is also the voice of Maria Rivera on Nickelodeon's El Tigre: The Adventures of Manny Rivera.