Leonard was immediately interested in dating Penny when she became the guys’ new neighbor. In the pilot episode of The Big Bang Theory, Leonard Hofstadter and Sheldon Cooper meet Penny after she moves into the apartment across the hall. Leonard is instantly attracted to her, while Sheldon is far less interested in socializing.
Leonard’s crush becomes one of the show’s central storylines. He tries to impress Penny, invites her to dinner, and gradually becomes part of her social world. Penny initially sees Leonard mainly as a friend and neighbor, and their very different personalities create much of the comedy in their relationship.
A common mix-up is Howard, who is also known for pursuing women, but he was not the character immediately focused on dating Penny. Leonard and Penny eventually date, separate, reunite, and marry during the series. Their relationship gives the sitcom a long-running romantic arc alongside its stories about science, friendship, and adult life.