I wonder if the movie Dave borrowed from this plot.
They are extremely similar, just with different twists.
shareIt would not seem too far fetched to believe they all are loosely based on the theme of The Prince and the Pauper. A poor insignificant nobody exchanges places (either forcibly or voluntarily) with a rich powerful/significant somebody because they "look alike."
King Ralph is also a story of an insignificant nobody being raised to a high position, although there is no "look alike" aspect of the story.
One could go back as far as the 16th century and examine how Shakespeare had pauper Christopher Sly duped into mistaking himself for a wealthy man during the introduction to “The Taming of the Shrew” -- a play rife with characters assuming another's role and mistaking each other's identities.
But then, Shakespeare probably got his plot from an earlier source.