Karen McCormick is the youngest member of the McCormick family. She first appeared as a background character in "Best Friends Forever". She later appeared in "The Poor Kid", where she played her first major role. Kenny is very protective of her, using his Mysterion identity to comfort her in hard times and keep her out of danger. Kenny's protectiveness extends to such a degree that she considers him her "guardian angel".
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, her jacket has no scrapes or tears, and she has no mittens. For pajamas, she wears a pink-collared light blue shirt with pink and purple hearts and pink bottoms, or a pink one-piece with magenta flowers.
In "The City Part of Town", her appearance has been slightly upgraded with her hair now tied back in pigtails and her face and jacket being messy again. Her Heidi-like hair was possibly used as a Placeholder hairstyle for animation testing.
In From Dusk till Casa Bonita, after becoming a vampire, her pig-tailed hair is styled differently (similar to the Emo Ponies hairstyle) and colored black with purple accents. She wears a black top with an image of a skull and crossbones on it as well as magenta pants and fingerless gloves. Her face still looks dirty as with her original form in the main game, though it is accented with purple eyeshadow makeup.
- To see images of Karen McCormick, visit Karen McCormick/Gallery.
Karen seems to be relatively quiet and timid, thus indicating shyness. She is almost always seen with Kenny. She is usually seen crying when dealing with stressful situations. When Mysterion is around, Karen seems to feel safer, since she does refer to him as her 'Guardian Angel'. Karen sometimes carries a pink princess doll around with her, or mostly stays around either Kenny, Kevin, or her mom. It seems that Karen is lonely and that she has very few friends, including Kevin and Kenny. In "The City Part of Town", when Kenny buys her a new doll, the first thing she does is start talking to it, possibly for social reasons. Karen also seems naïve as to what might harm her, as shown in "Naughty Ninjas", where she brings a syringe previously owned by homeless people back into her house.
Karen is Kenny's younger 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 and loves her dearly.
She is Carol McCormick's only daughter. She seems to love her mother, even after being through years of abuse likely due to her parents' fighting. She seems to go to her mother when she is scared, as shown in "The Poor Kid" when she's seen crying in her mother's arms when Stuart and Kevin are fighting. When she and her siblings are in The Soft Room, she immediately asks if she can see her mother.
In "The City Part of Town", she sits on her mother's lap at the gentrification meeting and sits close to her on their couch, asking her if they can eat at the SoDoSoPa. Carol seems to be more patient with her than Stuart, who immediately yelled at her about how costly ice cream is.
Carol McCormick also started yelling about Karen's protection when she brought in a syringe from the homeless in "Naughty Ninjas".
She is Stuart's only daughter. They have not interacted much, so little is known about their relationship. She seems to be scared of him, as shown in "The Poor Kid" when she cries when he and Kevin fight, and in "The City Part of Town" when she cowers and leaves the room after he yells at her.
However, Stuart shows that he does care about her, along with Kevin and Kenny, in "Naughty Ninjas" when he argues with the police about how the homeless living outside of their house are scaring the kids.
She is Kevin's sister. It is apparent that she is not as close to Kevin as she is to Kenny, since they have never been shown interacting one-on-one and she cries when he and Stuart fight in "The Poor Kid". However, in "Best Friends Forever", she is seen hiding behind Kevin in the hospital. It's likely that she trusts Kevin. In "The City Part of Town", it is shown that they share a bedroom.
- "Best Friends Forever" - Seen with her family at the amusement park and visiting Kenny at the hospital.
- "The Poor Kid" - Appears as a major character. First speaking appearance.
- "The City Part of Town"- Given a baby doll by Kenny.
- "Naughty Ninjas" - Screams when a homeless man threatens Stuart and listens to his phone call to the police.
- "PC Principal Final Justice" - Seen standing with Kenny and her parents when Randy confronts the Whole Foods.
- "Bike Parade" - Watches her father scolding Kenny.
- "Band in China" - Seen at the Autumn Fest.
Karen can be found in the McCormick house watching TV. She says that Princess Kenny texted her about how cute New Kid is, and asks the New Kid to protect her "sister" for her. She strangely never mentions Kevin in the game.
In South Park: The Fractured But Whole, Karen has been updated to her latest look, in similar vein to "The City Part of Town". She is available in her bedroom on Day 3 onwards in-game, whereby The New Kid can take a selfie with her after returning her doll, which can be found in the Soft Room of Park County Police Station.
Karen plays a major role in the From Dusk till Casa Bonita DLC. She is "kidnapped" by the Vamp Kids and brought to Casa Bonita, where she turns into a vampire. Mysterion and The New Kid try to rescue her. Along the way, she is possessed by Corey Haim, who was accidentally summoned by Mr. Adams. After he is defeated, she goes back to normal, and finally realizes how "completely fucking lame Vamp Kids are". Henrietta then teaches her how to be goth, by smoking a cigarette.
- If Karen is around 6 years old, that means that Mrs. McCormick gave birth to her when Kenny was around 3 years old, although we rarely see her anywhere in the house.
- In the original script for Starvin' Marvin, Kenny was referenced to have a sister but she never appeared in the finished episode.
- In more recent episodes, Karen is seen a lot more with her family, along with Kevin and Kenny.
- Karen's "vampire hair" is a kind of hair available for equipping in the game, but it's called "Emo Ponies" in the Costume app.
- Her vampire look greatly resembles Allison Mertz.
- The doll Kenny gave her is a parody of Baby Alive.