Leonard and Sheldon are brilliant physicists - geniuses in the laboratory, but socially challenged everywhere else. Enter beautiful, street-smart neighbor, Penny, who aims to teach them a thing or two about life. Despite their on-again, off-again relationship in the past, Leonard and Penny have finally gotten married. Even Sheldon has found a female companion, entering into a "Relationship Agreement" with neurobiologist Amy Farrah Fowler. In their free time, Leonard and Sheldon enjoy fantasy role-playing games with their ever-expanding universe of friends, including fellow scientists Raj, Howard and Howard's adorable microbiologist wife, Bernadette, who recently learned that they will soon be parents.