At the beginning of the film, Melvin Dummar sings a song that he has penned, "Santa's Souped Up Sleigh." He tells Howard Hughes that he sent the words - along with a sum of money - to the Hollywood Music Company, an outfit that puts its customers' song lyrics to music for a fee. Although Melvin doesn't realize it, the tune that the company used is not an original one: they paired his lyrics with the melody of "Wabash Cannonball."
Now listen buddy, you wanna do me a favour?
Howard Hughes: Depends on what it is.
Melvin Dummar: I wrote this song...
Howard Hughes: NO!
While the men are in the truck talking, a sandwich being eaten has the bite area alternately changing from one side of the bread between shots.