Kissin' Cousins (1964)
Kissin' Cousins is a 1964 American musical Panavision Metrocolor comedy film directed by Gene Nelson and starring Elvis Presley. Written by Gerald Drayson Adams and Gene Nelson, the film is about an Army officer who returns to the Great Smoky Mountains assigned to convince his kinfolk to allow the Army to build a missile site on their land. His mission is complicated when he meets his look-alike cousin and two beautiful country cousins who compete to win his affections. Presley played two roles in the film: the Army officer, with dark hair, and his look-alike cousin, with blond hair.
More at Wikipedia.