Kissin' Cousins (1964)

Directed by Gene Nelson. This Elvis Presley vehicle is without question the first movie I've seen in which the main character has a perfect double, a doppleganger (naturally also played by the film's star), yet this is in no way integral to the plot of the film. If you're aware of another, please let me know.

Josh Morgan, an Army officer (Presley) returns to the Smoky Mountains to convince his kin to allow the military to build an ICBM missile site on their homestead. When Morgan arrives, he realizes that it is impossible to resist that Yvonne Craig, who has an insane body even though her character may or may not be related to him. Yet definitely related is Cousin Jodie, whom we are able to distinguish from Josh because Jodie has blonde highlights and wears denim. Jodie is mountain's champion wrassler, and other hilarious things. Otherwise, he's irrelevant.

You're probably familiar with other films that involve characters with perfect doubles, such as "Vertigo" (1958), "Adaptation" (2002), "Black Swan" (2010) and several versions of "The Prisoner of Zenda." We could debate whether "The Parent Trap" counts because those characters were twins (I'd say no). Only in 2014, there have been four: "Enemy" (with Jake Gyllenhaal), "The Double" (with Jesse Eisenberg), "The Face of Love" (with Annette Bening) and the best of all of them, “Muppets Most Wanted” (with Kermit the Frog).

"Kissin' Cousins" is nothing like any of these because Jodie has nothing to do. It's also not like any contemporary film, which would involve an empathy-based story in which Elvis bonds with his family and decides to convince the military to relocate the missile site, possibly by way of a hilarious scheme that requires his perfect lookalike, Jodie. But no! Instead, this pure propaganda ends with everyone happy because Elvis' uncle was drunk enough on moonshine to sign on the dotted line and hand his land over to the U.S. of A. Really! Big dance number!