Question: where do the big bang theory characters live
Answer: The show originally centered on five characters living in Pasadena , California : Leonard Hofstadter and Sheldon Cooper , both physicists at Caltech , who share an apartment ; Penny , a waitress and aspiring actress who lives across the hall ; and Leonard and Sheldon 's similarly geeky and socially awkward friends and co-workers , aerospace engineer Howard Wolowitz and astrophysicist Raj Koothrappali .