Over time, several supporting characters have been introduced and promoted to starring roles, including Bernadette Rostenkowski-Wolowitz, Amy Farrah Fowler, Stuart Bloom, Emily Sweeney, and Leslie Winkle.The series also features numerous supporting characters, each of whom plays a prominent role in a small group of episodes.The writers have toyed with a romance between him and next-door neighbor Penny since the series premiere, with their unresolved sexual tension being a major force for drama.Leonard dated Penny for most of season three, although they had dated briefly at the end of season one.Aside from Penny, Leonard has had romantic relationships with co-worker Leslie Winkle, physician Stephanie Barnett, an unnamed French literature Ph D, and North Korean spy Joyce Kim.Following his break-up with Penny, Leonard began a relationship with Raj's sister Priya in season four, and it is implied they had a brief sexual encounter before the start of the series.
Compared to his friends, he is relatively successful with women.(Johnny Galecki) is an experimental physicist with an IQ of 173.Originally from New Jersey, he received his Ph D at age 24, spending at least some of his time at Princeton University.Included among them are parents of the main characters, their dates and their coworkers.
Celebrities such as Stephen Hawking occasionally appear in cameo roles as themselves.
The two attempted a long-distance relationship after Priya moved back to India, but Leonard eventually broke up with her in season five after she admitted to cheating on him with her former boyfriend.