From Wikipedia, the free encyclopedia. Mona Marshall (born Mona Mortica Ianotti on August 31, 1947) is an American voice actress. She is often cast in the role of young boys. Her roles have included parts in not only Japanese anime, but also in American cartoons as well. Mona Marshall has recently lent her voice to the talking bear Koby the Study Buddy. Her most notable roles are that of playing Sheila Broflovski, Linda Stotch, and additional voices on the popular television show South Park as w...