Professor Goldfarb is a Jewish physicist at Caltech, who objects to Sheldon's plans to solve the Middle-East Crisis by building an exact replica of Jerusalem in the middle of the Mexican Sonoran Desert in order to make a new promised land. He is seen discussing the matter with him at Dennis Kim's welcoming party, wearing a yarmulke. ("The Jerusalem Duality")
In "The Hamburger Postulate", Sheldon mentions to Leonard that he and Leslie could manufacture a Mr. & Mrs. Goldfarb, perhaps inspired by Professor Goldfarb.
Mentioned in "The Helium Insufficiency", when he used his grant money for a Russian girlfriend who lived in Van Nuys instead of using it to buy the electron microscope he was supposed to.