Lois is voiced by Alex Borstein. At the time series creator Seth MacFarlane approached her for a role on the show, she was doing a live stage show in Los Angeles, playing a redhead mother in a sketch. The voice style was modeled after one of her cousins' voice.
Born Lois Pewterschmidt, Lois was brought up in a extremely wealthy household with her sister, Carol. They also has a long-lost younger brother, Patrick, who was sent to a mental asylum after he became a serial killer. She met Peter when he was employed as a towel boy by her aunt. Her rich father cannot stand Peter and makes rude comments at every chance he gets. Peter seems to unintentionally do his absolute best to be a thorn in her side. She also alludes to have studied at Kent State University.
Lois is currently a full-time-mom and spends most of the working day caring for Stewie, cleaning the house and cooking food for her family. However, she is also a piano teacher on the side, to supplement the family income. She is currently 42. She is reportedly two years younger than Peter as claimed in "Let's Go to the Hop". However, this is slightly skewed by both Lois and Peter are 18 in "Meet the Quagmires" although only Brian's exclamation that she is 18 supports this.
Though initially appearing to be a typical doting house wife and ideal mother, Lois has many dark aspects to her and in some cases be worse than her husband, except without the excuse of mild retardation. Lois appears to have a taste for Sadomasochism (S&M), dressing as a dominatrix in "Let's Go to the Hop", putting out a lit cigarette on her arm in "Breaking Out is Hard to Do", asking Peter to put his finger in a bullet hole and twist it when he accidentally shot her in "Barely Legal" and directing Peter to kick her breasts in "Brian's Got a Brand New Bag". Several times Lois has forced Peter to have intercourse with her, yet she sees nothing wrong with this as she believes men can not be forced to have sex.
She has made it clear several times that she never wanted to be a mother. In "A Fish out of Water" when her and Meg go on Spring Break, during the awkward car-ride she tells Meg that she took birth control but taking antibiotics made it not work, evidently causing Meg's birth. In "Peter's Daughter" she instructs Meg on how to have a miscarriage". Chris was also said to be the result of a broken condom in "Emission Impossible", with the resulting lawsuit paying for the Griffin's house.
Her one-year-old baby Stewie is very much intent on killing her. Incidentally, this could be a direct result of smoking pot whilst pregnant with him. Her relationship with Meg is a complicated one. She has a way of being supportive and destructive at the same time. When being hurtful, she is extremely caustic. It's been said in "Screwed the Pooch" that Meg is not really Peter's daughter, but her biological father is named Stan Thompson.
However, in newer episodes, she now has a more non-caring personality and will often show absolutely no emotion or interest in some very emotional situations, and in other cases draw pleasure from others misery. Some examples being when Meg was upset about not being invited to a party hosted by Chris in "Stew-Roids", she just gives up, gives her daughter some pills and a Sylvia Plath novel, walks out stating "whatever happens, happens". Meg even stated she loved her in "Peter's Daughter", only for Lois to not even respond. When Brain was leaving in "Quagmire's Dad", she doesn't even look away from the television to state her goodbyes. Later in that episode when Quagmire was stating that his father wants a sex change operation, she leaves the room while stating "have fun at the circus" which could either be a cruel joke at Quagmire or barely paying attention to the conversation. She also has occasionally laughed at Brian such as when she and Peter laughed at Brian when he unknowingly had sex with Quagmire's father and did not bother to tell him why they were laughing at him. It is highly suggested this is due to Peter's constant antics which have severely worn her out throughout the series. In "Jungle Love", she also purposely drew attention to Chris so that he could be hazed on his first day of high school or gave Meg a school lunch in "Stew-Roids" consisting of nothing but food waste and a picture of herself eating a chicken leg.