The Hawking Excitation - S5-E21
Character mistake: The sign on Howard's laboratory door reads "RESTICTED area".
The Hawking Excitation - S5-E21
Continuity mistake: When Sheldon is trying to convince Howard to let him meet Stephen Hawking, Howard places a water bottle on the table he is sitting in front of. In the next shot, it appears in his hand again.
The Hawking Excitation - S5-E21
Continuity mistake: When Howard and Bernadette are in his bedroom, there is a bottle of Vitamin Water to Howard's left. In one of the shots, the bottle has completely vanished out of frame, but returns in the next shot.
The Hawking Excitation - S5-E21
Continuity mistake: Penny is talking to Sheldon in the laundry room and places a box of detergent on the machine. The side of the box is facing her. In the next shot, the box has turned to face her.
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