Patty Duke as Anna Marie Duke/ Patty Duke

Timothy Carhart as Harry

Howard Hesseman as John Ross

Deborah May as Ethel Ross

Ari Meyers as Patty Duke, as a youth

Millie Perkins as Frances Duke

Jenny Robertson as Patty, as a young adult

Arthur Taxier as John Astin

Matthew Perry as Desi Arnaz Jr.

Ray Duke as John Patrick Duke

Karl Malden as Doctor Harold Arlen