The Cooper Extraction - S7-E11
Continuity mistake: When Amy says that Penny never would have met Stan Lee, she draws a thick black line between "Penny" and "Stan Lee" on the board. The camera goes to Penny, and when it comes back to Amy, the line is blue and faint.
Chosen answer: The song is called "Dark as a Dungeon" and was written and first performed by singer-songwriter Merle Travis in 1946. It has been performed by a wide array of artists, including Tennessee Ernie Ford, Harry Belafonte, Dolly Parton, Queens of the Stone Age, Kathy Mattea and Amy Grant. But it was made most famous when it was performed and recorded by Johnny Cash during his concert at Folsom Prison in 1968. According to Wikipedia: "It is a lament about the danger and drudgery of being a coal miner in an Appalachian shaft mine. It has become a rallying song among miners seeking improved working conditions."
Michael Albert