The naturally black-haired Cartwright is best known as a child actress for her roles in the film THE SOUND OF MUSIC, as Danny Thomas's daughter, Linda Williams, in the 1950s TV series, MAKE ROOM FOR DADDY (a role she played from 1957 to 1964), and in the US television series as Guy Williams's and June Lockhart's daughter and middle child, Penny Robinson, in the 1960s cult sci-fi tv show, LOST IN SPACE. . how adorable was she!