Ferdin provided the voice of Lucy van Pelt in three Peanuts cartoons: the 1969 TV special It Was a Short Summer, Charlie Brown, a 1969 feature film A Boy Named Charlie Brown and the 1971 TV special Play It Again, Charlie Brown. Ferdin was a frequent guest star on episodic television in the 1960s and 1970s, with appearances on Bewitched, Green Acres, The Andy Griffith Show, Branded, Daniel Boone, Custer, The Monkees, The Flying Nun, Gunsmoke, Shazam!, The High Chaparral, Mannix, The Brady Bunch, Family Affair, Love, American Style, Marcus Welby, M.D., Sigmund and the Sea Monsters, Apple's Way, The Streets of San Francisco, Baretta, CHiPS, and 240-Robert.