At about the 14:15 mark Tip, John and Grandpa sing "Mademoiselle from Armentières," a WWI-era song considered to be quite risque, which explains Olivia's obvious discomfort.
When Tip arrives at the Waltons' house, he stands up in his car and announces, "Lafayette, we are here!" This is a famous quote from Col. Charles E. Stanton made at the tomb of French Revolution and American Revolution hero Marquis de Lafayette on July 4, 1917. In context Stanton said: "America has joined forces with the Allied Powers, and what we have of blood and treasure are yours. Therefore it is that with loving pride we drape the colors in tribute of respect to this citizen of your great republic. And here and now, in the presence of the illustrious dead, we pledge our hearts and our honor in carrying this war to a successful issue. Lafayette, we are here."
Tip's car is a 1930 LaSalle Convertible Coupe.
As John-Boy and John take a break from unloading the lumber, a poster advertising a dance marathon is seen behind them. John-Boy would go on to enter a dance marathon in The Marathon (1974).