Karen McCormick

Karen McCormick is the youngest member of the McCormick family and appeared as a background character in "Best Friends Forever". She played a bigger role in "The Poor Kid" as the episode is focused around the McCormick family. She is very shy and timid, Kenny is very protective of her and uses his Mysterion identity to comfort her in hard times, to such a degree that she considers him her "guardian angel".

Development
Although early press materials for the first season described Kenny as having a sister, whose design was supposedly similar to Ike's according to South Park Studios moderator Willie Westwood, and the original script for the episode "Starvin Marvin" by Trey Parker, as published at South Park Studios in 2001, mentioned a sister in the final scene at the McCormick family dinner, no sister appeared on the show for several years, and it was generally accepted the family was limited to a mother, father, and two sons. In "Best Friends Forever" she appeared briefly with her family at an amusement park and at the hospital visiting her brother, but she never speaks or is referred to in dialogue, and is generally hiding partly behind Kevin McCormick. She wasn't seen with her family in "The List" or "Sexual Healing", leading her to be somewhat forgotten, although some fans embraced her. The name "Karen" first appeared on Wikipedia, attributed to Matt Stone. She finally played a role in the series in "The Poor Kid", which focused on her and her brother's close relationship after their parents are arrested. She is shown to be very shy and timid, and a target for bullying, and as a result her brother is protective of her, using his Mysterion identity to comfort her when she is sad (much as he uses it to manipulate his parents) and later to save her from a bully at school. She refers to him as her "guardian angel".

Appearance
She looks very similar to Heidi Turner, with the same hairstyle, although a darker shade of brown closer to her father's color, and a green jacket like Heidi's, but with a plum collar and mittens instead of red ones. In her first appearance, she has dirt over much of her face, and her hair is slightly messier, but by her second appearance, she is clean besides dirt over her left eye. For pajamas, she wears a blue shirt with hearts and pink bottoms. It seemed strange that she was wearing pajamas at all, since it's known she lives in a very poor family. It's possible she got them from her foster parents, or another foster child. She appears to be the size of a first or second grader, though few children this age appear on the series, making it difficult to tell. Her appearance was significantly cleaned up in "The Poor Kid" - her jacket no longer has the scrapes or tears, her face is not as dirty and her hair is not as messy.

Personality
Karen seems to be relatively quiet and timid, indicating shyness. She is also very childlike, but considering her age, this is normal. She is almost always seen with Kenny. She seems to be very attached to her doll, as she brings it with her everywhere she goes. She usually cries when dealing with stressful situations.

Kenny McCormick
She is Kenny's sister.She seems to have a good relationship with him, especially his alter-ego, Mysterion, to such an extent she considers him a "guardian angel". She also seems to look to Kenny for protection and comfort when she is upset; this is shown when The McCormick Siblings are in The Soft Room at the police station, and Karen is clutching Kenny's arm. Kenny is extremely protective of her.

Mrs. McCormick
She is Mrs. McCormicks daughter. She seems to love her mother dearly, even after being through years of abuse through her parents' fighting. Karen can be seen being held by her mother, crying, when her father, Stuart, and her oldest brother, Kevin, are fighting, showing that she seems to go to her mother when she is scared. When all three McCormick children are seen in the Park County Police Center's "Soft room" She is seen crying, asking if she can see her mother.

Stuart McCormick
She is Stuart's daughter. They have never interacted one-on-one, so little is known about their relationship. It is likely she dislikes her father, due to his abusive personality.

Kevin McCormick
She is Kevin's sister. She seems to not be as close to Kevin as she is to Kenny, as she hold Kenny's arm in The Soft Room in the episode "The Poor Kid". This is probably due to Kevin's constant fighting with their father, and getting them taken away from their parents.

Prominence

 * "Best Friends Forever"
 * "The Poor Kid"- Appears as a major character. First speaking appearance.