She is of Polish origin and Catholic upbringing, and is frequently seen wearing a cross necklace. Most notably, she is one of the only characters in the show who can control Sheldon, mostly because of her knowledge in dealing with stubborn children. She is generally a friendly and good-natured individual, quickly making friends with Penny and Amy, as well as the rest of the gang, but occasionally shows signs of mania, most notably when she got into a fight with Amy over a parking space Sheldon and Howard were fighting over, and when she explains her interest in microbiology as being because she feels like a God to the bacteria she is studying.
Bernadette was first introduced to Howard by Penny after he invoked the "Girlfriend Pact". At first, she and Howard do not get along, as they appear to have nothing in common. When they find out that they both have overbearing mothers, they feel a connection. Subsequently, Howard realizes Bernadette presents a real opportunity to develop a lasting relationship and, in an impulsive manner, he proposes to her.Although Bernadette rejects his offer, they remain a couple for a time after Howard sings a heartfelt song for her at the Cheesecake Factory, which Penny finds quite embarrassing, but Bernadette finds romantic. Eventually they break up when she discovers Howard using his avatar to have sex with another online character in World of Warcraft. Bernadette and Howard reconcile and resume their relationship, ultimately culminating in their engagement in the season 4 episode, "The Herb Garden Germination".
In "The Roommate Transmogrification", she finally obtains her Doctorate and is subsequently hired by a pharmaceutical company with a high salary. This makes Howard jealous, especially after the rest of his friends taunt him about his lack of a Doctorate, and eventually leads to them having an argument after she purchases a Rolex watch for Howard, which he interprets as her "rubbing in" the fact that she now earns more than him.
Howard later learns that Raj fantasizes about Bernadette and writes love poems about her. Bernadette almost breaks up with Howard after hearing about his previously unknown former sexual escapades that came out during his bachelor party from the episode "The Stag Convergence". Howard and Bernadette are married (by the entire main cast) on the roof of the apartment that day before he has to go into space. During season 6 the newlyweds do have some bumps, including Howard readjusting to being back on earth, moving out of his mother's house,and again when he spends too much on his collectibles hobby.