From Wikipedia, the free encyclopedia. Margaret Julia “Marlo” Thomas (born November 21, 1937) is an American actress, producer, and social activist known for her starring role on the TV series That Girl (1966–1971). She also serves as National Outreach Director for St. Jude Children's Research Hospital. Description above from the Wikipedia article Marlo Thomas, licensed under CC-BY-SA, full list of contributors on Wikipedia.