When Sheldon alerts Penny that she'll earn over $3,000 for a single night of work, she imemdiately goes to buy shoes.

Amy is mad at Sheldon, and he goes to the jewelry store with Penny to buy Amy something. Sheldon hints to the salesperson that diamonds are carbon just like charcoal, but it's only their molecular arrangement that makes them valuable. When the salesperson tells Sheldon that everything is on sale, Sheldon is suddenly more interested in a pocket watch he was previously considering.

Beaver and his brother are given an introduction to the world of stocks and bonds by their parents. Their father patiently answers the eager boys' questions.

In this clip, the main mathematical concepts derive from a field called game theory. The goal of game theory is to take some social situation with some notion of winning and come up with a formal, mathematical way of discussing it.

In Fear the Boom and Bust, John Maynard Keynes and F. A. Hayek, come back to life to attend an economics conference on the economic crisis.