Kym Karath began her acting career at the age of 3, appearing in Spencer's Mountain (1963) with Henry Fonda and Maureen O'Hara, The Thrill of It All (1963) with Doris Day and James Garner, and Good Neighbor Sam (1964) with Jack Lemmon, before winning the role of "Gretl", the youngest Von Trapp daughter. After The Sound of Music (1965), Kym ...