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, and he recently took their relationship to the next level by proposing marriage. 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 is adjusting to life with their new baby girl.