Kitty is married to Red Forman and is mother to daughter Laurie, with whom she has a stressful relationship, and son Eric, whom she has a habit of overprotecting, even to the point of saying that his girlfriend Donna Pinciotti seduced her "poor boy and tricked him into having sex with her" in "Parents Find Out", which could not be further from the truth.
Kitty is the one who convinces Red that they should take in Steven Hyde in Season 1, after Hyde's mother leaves him. She likes to give off an appearance of goodness and be everyone's favorite mom in the neighborhood, though in later seasons Kitty is revealed to have a somewhat dependent relationship with alcohol. Kitty works at the Point Place General Hospital, where patients such as Michael Kelso, Steven Hyde, Fez and Red Forman have been hospitalized. Despite being a nurse and knowing the consequences of her actions, Kitty smokes and has tried to quit on several occasions to no avail.
Kitty is a caring mother and is usually a caretaker for the neighborhood kids. She is generally a nice person except when either stressed out or annoyed. Whenever stressed out, Kitty normally does her famous laugh in a shrill voice, squints her eyes, or makes sarcastic remarks (akin to Eric). Kitty's family hails from Sweden; she mentions that her grandmother, who had a thick accent, is from Sweden, in the episode Streaking.
Kitty has a strained relationship with her mother, while endlessly trying to please her mother, in her heart, Kitty loves her. Bea says she never went through menopause, and when Kitty needed guidance and help from her mother, Bea refused. When her husband dies, Bea acts as if though she does not care about Burt's passing, yet Kitty finds her crying in her bedroom the night of the funeral.
Kitty has a better relationship with her father, Burt hides from his wife because she is shrill, uptight, and yells constantly. After going bankrupt, the Sigurdsons moved from Arizona to live with the Formans. Burt bought an ostrich farm right next to a coyote farm. The coyotes ate all their ostriches and they lost all their money. While living with the Formans, in Your Time Is Gonna Come, Burt has a heart attack in their driveway and eventually dies at the hospital that same night.
Kitty typically supports Eric against Red and often scolds Red for being too hard on Eric. However, she also does not consider Eric to be a man and often refers to him as her "precious baby boy." Eric appreciates his mom's support but her overblown displays of affection often leave him feeling embarrassed. At times, Kitty's love for Eric borders on Hitchcockian. His mother is often insecure about being replaced by Donna as the woman in Eric's life. Their rivalry is played up in many episodes (often comically, but sometimes to the point of it being a problem). In theory, she is okay with a sexual relationship between Donna and Eric, even pressing the two to discuss it with her, but in reality she goes into a depression after learning that Eric and Donna had sex and considers Donna a harlot who stole her baby boy away from her. Eric assured Kitty he would always need her because, "Dad's going to be riding my ass for the rest of my life!"
When Eric tells his parents about his plan to teach in Africa for a year, his mother is less than thrilled. This is most notably, and comically presented when, the morning after his announcement, Kitty fixes everyone at the breakfast table a smiley-face breakfast with eggs and bacon and then hands Eric a plain pancake with, "nothing smiling up at you, nothing." Even with a couple days before his departure, Kitty reveals that she hid mailed notifications that Eric must receive certain vaccinations before his departure. Eric protests his mom's actions but she still tries to dissuade him stating that the needles used for the vaccinations are really large and will hurt a lot. After Eric disobeys his parents' orders not to go forward with his marriage to Donna, Red finally deems Eric a man and offers his blessing while a devastated Kitty turns on Red for allowing her "precious baby boy" to get married.
Whereas Red favors Laurie over Eric (at first), or at least is hard on Eric while lenient with Laurie, Kitty is onto Laurie and calls her bluff time and again, at times preventing Laurie from going out partying with random guys. Though Kitty sometimes remarks that she always considers Donna the daughter she "never had" and refers to Laurie as a worse baby than Rosemary's, Kitty loves her daughter deep down and, after many lies and schemes endured, still tries to help Laurie when she decides to attend cosmetology school.
In Season 5, Kitty told Red that she was pregnant, only to go to the doctor who told her the reason why her periods had stopped was because she was beginning menopause. To help his wife through menopausal mood swings, Red got Kitty a wiener dog she named Schatzi (German for Little Treasure). Mood swings occurred often with Kitty (ex. The Formans' were going to visit the University of Wisconsin and she says that she is "freakin' old!") Kitty tries to control it or if she says something rude she usually blames it on the menopause, saying "Oh, that was not me. That was the menopause talking!"
In Season 8, Kitty burns off part of her hair from candles as she tried to strip for Red. Sam had taught Kitty to strip "step, dip, hair, flip." When Kitty tried it for Red in the living room, she flipped her hair and a candle caught it on fire. Her hairstylist said there was not enough hair to salvage her old hairstyle. It was cut shorter, and Red found it attractive.
After Eric left, Kitty taped everything that the gang did for Eric to hear and she had a choice of either staying in Point Place, or Red's decision to move to Florida with Bob. During the last of the 8th season, she tried to persuade Red into staying in Point Place, but he thought she wanted to leave, so he did everything he could to try to move. He and Kitty also put Hyde's rent in a checking account for him since they were supposedly going to move. She was also the only one to show the entire main floor, something that has not been done on the series.
- Kitty's paternal grandmother is from Sweden (Sigurdson is a Swedish surname).
- It is unknown, yet possible, that Kitty and Paula have a brother, as Kitty's niece Penny visits in Season 4, but it is never alluded to that Paula has any children. Penny and Eric are also shown to be the same age.
- Kitty is apparently an Elvis Presey fan: When Kitty feels hurt and insulted, she goes to bed for a long period of time and when this occurs, Red mentions that the last time she did so was when "Elvis died on the crapper".
- Kitty's cigarette smoking was slowly phased out after Season 3, due to Debra Jo Rupp kicking the habit in real life.
- In the Season 3 episode, Kitty's birthday would have been Thursday, October 13, 1977. This can be deduced given that Red said it was the 13th and they were watching "The Waltons" and then "CHiPs" both broadcast on a Thursday night. The only Thursday night that fell on the 13th in 1977 after CHiPs debuted date on Sept. 15th would have been October 13th. Also to note: CHiPs that night was "Moving Violation"; The Waltons was "The Warrior".
- Michael once called Kitty a "hot mom".
- Debra Jo Rupp had been asking for a new hairstyle for Kitty and so the writers wrote it into the show in season 8.
- Kitty had a bigger role in Season 8 after Eric and Kelso left.
- Kitty seems to like Neil Sedaka, she has been seen listening and singing to Bad Blood on the radio in the Toyota on the way home from work with Eric in Career Day