Stephanie Barnett

Dr. Stephanie Barnett is a doctor and highly distinguished surgical resident at Fremont Memorial Hospital. She is one of Leonard's ex-girlfriends.

Character Information
Stephanie made her debut in The Lizard-Spock Expansion, where she is shown to be a romantic interest of Howard, who tries to seduce her by taking her to his lab and have her drive a Mars rover. But when he sticks the space car in a ditch, he calls his friends over for help and asks Leonard to drive Stephanie home. This proves to be lethal for Howard's chances with Stephanie, as she and Leonard end up making out in the car. She eventually confesses to Howard how she's interested in Leonard and not him, which Howard takes as Leonard's betrayal of his trust. Howard starts considering Leonard to be dead to him, and insists his friends do the same around him. However, he forgives Leonard and Stephanie when he learns that they will help him meet Stephanie's roommate Lisa.

Stephanie continues dating Leonard, which leads to several encounters between her and Sheldon. Although she seems to put up with Sheldon's obnoxiousness, she uses her cunning to keep him under control. For instance, she makes him believe he has to stop talking because of his inflamed larynx in The Vartabedian Conundrum, which keeps Sheldon mute until the end of the episode.

By The Vartabedian Conundrum, she has established herself in Leonard's apartment, which leads to Penny pointing out that he and Stephanie are living together. The relationship is moving too quickly for Leonard, who insists she re-locate to her own apartment. He does, however, have trouble shaking her off, since when he tries to talk to her, she makes sexual advances on him and the two end up having sex. Although it's not seen on camera, it is known that some time between "The Vartabedian Conundrum" and the following episode "The Bath Item Gift Hypothesis", that she and Leonard broke up, but it is unknown who caused the break up and why. Leonaed is seen texting her supposedly asking her to move out. It is also unknown what has become of her and if she and Leonard continue to be friends.

Leonard Hofstadter
Main article: Leonard and Stephanie 

Stephanie's primary role in the show is being Leonard's girlfriend. They met in The Lizard-Spock Expansion, and continue dating for two additional episodes. Eventually it seems they broke up, but it is unknown why and when.

Trivia
.
 * Stephanie did her medical internship at Lawrence Memorial (fictional) in Galveston, Texas, which is where Sheldon was born.
 * Of all of Leonard's exes (Joyce Kim, Priya Koothrappali, Leslie Winkle and Penny), she is mentioned the least amount of times by the cast.
 * Stephanie was mentioned only one time since her breakup with Leonard in the Apology Insufficiency, when Sheldon mentions that Howard got the Mars rover stuck to impress her. It should also be noted that Sheldon didn't even refer to her by name.
 * Only girlfriend of Leonard's that Sheldon really liked.