The Einstein Approximation - S3-E14
Continuity mistake: When Sheldon is looking for another job, the woman is holding a piece of yellow paper up. Camera cuts and she is no longer holding the piece of paper.
The Einstein Approximation - S3-E14
Continuity mistake: When Sheldon is playing in the ball pit and Leonard is trying to coax him out the position of the black netting of the ball pit alternates between being and not being wrapped around the yellow entrance pillars.
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