Revealing mistake: Throughout the series much is made of the fact that Howard's mother is grossly obese, and in The Engagement Reaction (S4 E23) it is even mentioned that her arms are hugely oversized. However, at the end of this episode we see her arms when she grabs Raj to stop him climbing out of the window, and they are the arms of an average-weight woman - they aren't overweight at all.
Plot hole: In Series 1, Episode 7, "The Dumpling Paradox, " Sheldon makes an oblique reference to his financial status: "Frankly, if I could afford the rent, I'd ask you [Leonard] to leave, " meaning he cannot pay the rent on his two bedroom apartment by himself - not that he doesn't want to, he can't. However, in "The Execlsior Acquisition, " we find that he does not even cash his pay cheques. He doesn't even deposit them into a bank account - he leaves them in a drawer in his desk. In Series 2 Episode 14 "The Financial Permeability", he lends Penny a large amount of money from a huge bankroll he just happens to have lying about - again, without cashing his pay cheques! He is obviously independently wealthy. Either he doesn't have enough money to afford the rent or he has enough to work without being paid while practically giving large amounts of cash away. Can't be both.
Suggested correction:He doesn't say he can't financially afford the rent; he may have meant emotionally or functionally. He may feel that he needs the social support from living with other people. He couldn't afford not to have them with him.
What nonsense. He says, "Frankly, if I could afford the rent, I'd ask you to leave." If I could afford the rent – he is talking about money, not some vague, waffly jibber-jabber about emotional support.
He definitely meant emotionally. I just watched a random clip on YouTube from when Penny and Leonard were wanting to move in together and Sheldon lost it (and they mention it's not the first time). Saying he couldn't afford it is his excuse because he wouldn't admit (at that time) that he would be devastated.
Trivia: In this episode, Sheldon and Amy are trying to decide on couples' themed Halloween costumes. Sheldon is standing in front of the dry erase board. There are 2 columns written on the board. One named "Couples I Like" and the other "Couples You Like." Under the "Couples You Like" column, one of the couples is Blossom and Joey. Blossom is the name of the television character played by Mayim Bialik in the 90s and Joey was one of her brothers.
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."