The domed building visible from Leonard and Sheldon's apartment window is the Pasadena City Hall.
Sheldon refers to Penny as "Typhoid Penny" when inquiring as to which pathogen she has introduced as an analogy to "Typhoid Mary". Mary Mallon was a carrier of typhoid fever and many people she came into contact with died of it, although she showed no symptoms.
In the German dubbed version, Sheldon's line about Czechoslovakia and the Blitzkrieg were changed to refer to Poland.
Febrile Delirium is a symptom of disordered central nervous system function, with excitement, restlessness, and disorientation accompanying some acute fevers.
The waitress who warns Penny about the "homeless crazy guy at table 18" is the same woman who Raj met and went home with at Penny's Halloween party in The Middle Earth Paradigm (2007).