Penelope "Penny" Hofstadter is a fictional character from the American CBS sitcom The Big Bang Theory, portrayed by actress Kaley Cuoco. She is the primary female character in the series, befriending her neighbors Leonard Hofstadter and Sheldon Cooper, two physicists employed at the California Institute of Technology (Caltech).

Leonard Leakey Hofstadter, Ph.D., is a fictional character portrayed by Johnny Galecki in the CBS sitcom, The Big Bang Theory. Leonard is an experimental physicist who shares an apartment with colleague and best friend, Dr. Sheldon Cooper. For his portrayal, Galecki was nominated for a Primetime Emmy Award and a Golden Globe Award in 2011.