A member of the Cows Cheerleaders and one of the popular girls in the fourth grade class, Heidi is highly sociable and seems to spend a lot of time following trends along with the other girls. She seems to greatly values her social standing with them, sometimes to a fault when she becomes worried about damaging her reputation. Heidi is often sweet and sociably friendly, but her insecurity can sometimes lead her to be unkind to others.
Heidi can be superficial and even cruel, such as becoming angry when her mother insisted that she invite Marjorine to her slumber party with the other girls, and leading the other girls in bullying Marjorine when she exhibited strange behavior. She has also shown herself willing to throw others under the bus to try to save her reputation.
She became a target of Skankhunt42's cruelty on the South Park Elementary message board, and was the first of the girls to sit down during the National Anthem as a result.
- "I learned that betrayal can actually make your friendships stronger, and it's all thanks to you!" (South Park: The Stick of Truth)
During season 4, as Marcie, she was depicted with two generic background characters as parents - when her father, Steven Turner, took issue with her role in Cartman's Church, he was killed and sent to Hell.
In "Marjorine", recast as Heidi Turner, she was depicted with two new parents, a muscular blonde man and a woman with reddish hair. Though most fans simply consider this a continuity error, some fans speculate that her mother remarried, and possibly changed her appearance. These parents have sine made additional appearances.
Heidi was partnered with Cartman for the fourth grade egg project and despite mutual dissatisfaction with the initial choices, the two took care of their egg and when Cartman broke it, he asked Mrs. Garrison to give Heidi a better grade... probably in hopes of averaging it for both of them. Cartman also got four days of detention from PC Principal for calling Heidi "clitty litter", which was surprisingly, enough to temporarily break his spirit for misbehavior at school.
Heidi has since accused Cartman of being skankhunt42, a troll that has been sexually harassing her and other girls, in “Member Berries”, but Cartman is shown trying to defuse the situation instead.
Like most of the girls, he exhibited a notable attraction to Bridon Gueermo, whether he's singing or playing basketball.
Heidi is friendly with many of the girls, particularly the Cows Cheerleaders, but has not been shown to be particularly close to any of them. She invites most of them to her sleepover party.
- Rainforest Shmainforest (s03e01; debut cameo)
- Spontaneous Combustion (s03e02, cameo)
- South Park: Bigger, Longer & Uncut (cameo)
- Tweek vs. Craig (s03e05, cameo)
- Hooked on Monkey Phonics (s03e13, cameo)
- Mr. Hankey's Christmas Classics (s03e15, cameo)
- Do the Handicapped Go to Hell? (s04e09)
- Probably (s04e10; first identified as Marcy)
- Helen Keller! The Musical (s04e14)
- Proper Condom Use (s05e07)
- Bebe's Boobs Destroy Society (s06e10, cameo)
- It's Christmas in Canada (s07e15, cameo)
- Stupid Spoiled Whore Video Playset (s08e12)
- Marjorine (s09e09; first identified as Heidi Turner)
- Follow That Egg! (s09e10)
- Cartoon Wars Part I (s10e03, cameo)
- The List (s11e14)
- Eek, A Penis! (s12e05, cameo)
- Super Fun Time (s12e07, cameo)
- Breast Cancer Show Ever (s12e09, cameo)
- Elementary School Musical (s12e13)
- The Ring (s13e01, cameo)
- Eat, Pray, Queef (s13e04, cameo)
- Insheeption (s14e10, cameo)
- Funnybot (s15e02, cameo)
- Reverse Cowgirl (s16e01, cameo)
- Cash For Gold (s16e02, cameo)
- Faith Hilling (s16e03, cameo)
- Jewpacabra (s16e04, cameo)
- Butterballs (s16e05, cameo)
- Cartman Finds Love (s16e07, cameo)
- Raising the Bar (s16e09, cameo)
- A Scause For Applause (s16e13, cameo)
- Let Go, Let Gov (s17e01, cameo)
- World War Zimmerman (s17e03, cameo)
- Taming Strange (s17e05, cameo)
- Ginger Cow (s17e06, cameo)
- The Hobbit (s17e10)
- Stunning and Brave (s19e01; mentioned)
- Member Berries (s20e01)
- Skank Hunt (s20e02)
Heidi Turner appears in the girls' secret base as part of the Pleases and Sparkles Club. The player is assigned to discover who the secret "two-faced bitch" in the club is in order to complete the "Recruit the Girls" quest, and it's eventually revealed to be Heidi, as the translated abortion records reveal that her mother had been to the abortion clinic. However, the girls soon forgive her since she's really sorry, and she adds Douchebag on Facebook.
- In her early appearances throughout season 3, she has black hair instead of her usual mousy brown.
- Despite being one of the most prominent of the girls, her appearances in the background have dwindled in recent years.
- From seasons nine through seventeen, she bore a resemblance to Karen McCormick, Kenny's sister, though she began wearing hairclips.