The Cooper Extraction - S7-E11
Trivia: Penny gets her break appearing in NCIS. Kunal Nayyar who plays Raj, had his first acting job on NCIS season 4 episode 12 Suspicion. Coincidentally this is the episode prior to Penny's episode.
The Mommy Observation - S7-E18
Trivia: The car parked left from Stuart in the future sequence is a BMW i3, which is an actual production car introduced in 2014.
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