Theresa is a female fourth grader at South Park Elementary. She played a minor role in "T.M.I.", where she asked Randy Marsh: "What's a penis?". She plays a more significant role in the Season Twenty-One episodes, "Doubling Down", and "Moss Piglets."
She is usually shown with black hair, however, in her speaking role in "T.M.I.", she had brown hair. She wears a light orange, long-sleeve shirt, a blue vest, and a dark green skirt. She also has green hair ties, which she uses to put her hair into two puffy pigtails. She is currently the only known student to wear a vest.
She seems to be one of the more innocent fourth graders. An example of this is her lack of sexual knowledge, as shown in "T.M.I.". This is in contrast to most of the fourth grade girls, excluding Annie, many of which have been shown talking about some sort of sexual relation.
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- "The List" - She was shown as a member of the List-making committee.
- "Tonsil Trouble" - Seen in the background on the playground.
- "Super Fun Time" - Seen as Girl with Pink Sweater's partner during the field trip.
- "Elementary School Musical" - She was shown singing and dancing.
- "T.M.I." - Her first speaking role; she was shown in the classroom for the first time. She asked Randy Marsh, "What's a penis?" while he is explaining his flawed version of the T.M.I. formula.
- "Ass Burgers" - Cartman sells her a burger.
- "Butterballs" - Seen at the school assembly.
- "Cartman Finds Love"
- "A Scause For Applause" - Seen in the background in the school hallways talking to Kevin Stoley.
- "Let Go, Let Gov" - Seen in the playground.
- "World War Zimmerman"- Seen on the playground turning the jump-rope for Butters.
- "Taming Strange" - Briefly seen in the background in the lunchroom.
- "Gluten Free Ebola" - Seen at the boys' big party, talking to Kelly Pinkerton-Tinfurter.
- "Stunning and Brave"
- "The City Part of Town"
- "You're Not Yelping"- Seen in the hallway.
- "Truth and Advertising"- Seen in the cafeteria.
- "Member Berries"- Seen at the school assembly.
- "Skank Hunt" - Conspires with her fellow female classmates to get back at the boys for Skankhunt42's wrong doings.
- "Wieners Out" - Seen in the stands at the volleyball game.
- "Douche and a Danish" - Seen in the battle between the girls and the boys.
- "Hummels & Heroin" - Rallies with Marcus Preston after witnessing his presentation in the school cafeteria.
- "Doubling Down" - Later takes Heidi out to eat with the other girls. Teases her for her relationship with Cartman, although playfully, she makes very harsh comments and unintentionally hurts Heidi's feelings.
- "Moss Piglets" - Eats with the girls at lunch. Teased by Heidi at the bus stop for living in a trailer park.