Originally from New Jersey, Leonard is a Caltech experimental physicist who shares an apartment with Sheldon Cooper in Pasadena, California. He is usually seen wearing his characteristic black framed glasses, low-cut, black Converse All Stars sneakers, neutral colored sweat jackets, brown trousers, and physics-themed t-shirts.
Although Leonard feels at home with his geek colleagues, he wants to be more social. Among the main characters, he generally has the least amount of difficulty interacting with ”non-geek” individuals. He is instantly captivated by the presence of Penny, and from the beginning sets out to date her.
Having lived with Sheldon for several years, Leonard knows him best, and is obligated to explain Sheldon’s behavior, and serve as a mediator between him and other people in many situations. For instance, when Penny and Sheldon engaged in fierce dispute, Leonard gave Penny the phone number of Sheldon’s mother so she would call her son and scold him for his behavior, thus ending the fight.
Leonard can also play the cello. As seen in the season 1 episode ”The Hamburger Postulation”, he and Leslie Winkle practice their instruments and then leave to have sex.
Despite his attempts to not appear to be a geek, Leonard owns, among other things, Star Wars hygiene products, an expansive Superman comic book collection (and wears Clark Kent type glasses) and a Battlestar Galactica Colonial warrior’s flight suit. Early in the series, Leonard tried to get rid of his collectables to show maturity and impress Penny. However, he changed his mind when he saw Penny was already dating another man.