Continuity mistake: When Sheldon is sitting with Raj in his apartment watching television, the can of soda on the table in front of him rotates itself a couple of times. (00:14:40)
The Griffin Equivalency - S2-E4
Continuity mistake: In the opening scene, just after Howard says, 'Creepy good or creepy bad?', there is a shot where Howard is holding his food, even though Leonard hasn't given it to him yet and it isn't there in the shot before or after. After Leonard gives the food to Howard, the exact same shot is used after he says, 'I'm not necessarily talking about the food', so the shot was taken from there and it is shown twice. (00:00:25)
The Work Song Nanocluster - S2-E18
Continuity mistake: When Penny puts the box down at the start it is closed. Camera cuts and it's open instantly.
The Vartabedian Conundrum - S2-E10
Continuity mistake: When Sheldon is talking via the laptop, the amount of letters in the words he says is different to the amount of keys hit.
The White Asparagus Triangulation - S2-E9
Continuity mistake: When Leonard is helping Sheldon open the jar, the red napkin which he left on the couch where he was sitting changes position or vanishes in every shot.
The Lizard-Spock Expansion - S2-E8
Continuity mistake: At the very beginning, Leonard's Diet Coke keeps changing position without anyone touching it.
The Killer Robot Instability - S2-E12
Factual error: M.O.N.T.E. would not be able to knock down the door as he does at the end.
The Vegas Renormalization - S2-E21
Continuity mistake: When Leonard and Raj are getting ready in the bathroom, Raj picks up a tube of shampoo/conditioner off the bathroom bench with his left hand. However, in the next shot, Raj has nothing in his left hand and the tube is back on the bench, with no time for him to replace it between shots.
The Killer Robot Instability - S2-E12
Revealing mistake: Near the end of the show, the big robot is chasing the other robot down the hallway. The camera starts to zoom in as the robots come by it. The big robot stops just before the camera zoom is past it, yet they keep running down the hallway like the robot is still going.
The Bath Item Gift Hypothesis - S2-E11
Continuity mistake: When Leonard gives Penny her christmas gift, as she unwraps it she tears the paper off so that most of the box is exposed. In the next shot much more of the wrapping is back intact and differently positioned. (00:19:40)
The Killer Robot Instability - S2-E12
Revealing mistake: When M.O.N.T.E. crashes through the door at the end, the door hits the wall on the other side of the corridor. The wall shakes, revealing it's a set.
The Lizard-Spock Expansion - S2-E8
Continuity mistake: When Leonard is talking to Penny in the laundry room; as he walks forward to ask her about whether him dating Stephanie is wrong, the box of washing powder on the machine behind him alternately has its lid closed or open. (00:14:00)
The Barbarian Sublimation - S2-E3
Continuity mistake: When Leslie and Sheldon are talking to Dr. Eric Gablehauser in his office, in one shot Eric throws a piece of paper onto the desk behind him (next to the computer.) Through the rest of the scene, this piece of paper keeps changing position. (00:09:00)
The Financial Permeability - S2-E14
Continuity mistake: When Sheldon asks Penny if he lent her enough money, the container he is holding opens on its own. (00:09:25)
The Vartabedian Conundrum - S2-E10
Continuity mistake: When Stefanie and Leonard are talking in bed towards the end, Stefanie's arm moves from on her head to on her pillow instantly. (00:16:30)
The Euclid Alternative - S2-E5
Continuity mistake: When driving down Euclid Avenue, the background is constantly changing between shots. In one shot it's a busy main street and in another it's a suburban street. (00:04:50)
The Euclid Alternative - S2-E5
Continuity mistake: When Penny turns on to Euclid Avenue, the car behind her just vanishes into thin air. (00:03:50)
The Vartabedian Conundrum - S2-E10
Visible crew/equipment: When Sheldon and Leonard are making breakfast, stage lights are reflected off a milk bottle.
Continuity mistake: Right at the start of the episode, Leonard kisses Penny. When he starts kissing her his head is tilted to the right (opposite side to the wall with the camera). When they move to the camera image, his head is tilted to the left (on the side with the camera), and when they move back his head is back tilting to the right again. (00:00:30)
The Lizard-Spock Expansion - S2-E8
Continuity mistake: When Raj says Star Trek 5 is worse than Star Trek 1, his hands are outspread. Camera cuts and now they are clasped together. (00:04:15)
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