The Excelsior Acquisition - S3-E16
Character mistake: When Howard finds the stack of paychecks in Sheldon's drawer and wonders why Sheldon hasn't cashed them, Sheldon explains that he's saving them to purchase items that have yet to be invented and he doesn't trust banks. But just keeping them in his drawer doesn't do anything, because checks are voided after a set period of time and they would eventually become worthless.
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