Trixie is the daughter of Annie Young, the school nurse. She is more insane and mischievous than Junior, as she carries a lighter and M-80 dynamite sticks with her. She first met Junior when he popped her balloon with a slingshot from his father's car and laughed.
On the first day of school, she puts on a sign on his back, flipped him and drew a marker mustache on his upper lip, and sprayed him with a fire hose. Junior retaliated by making her throw up all over an amusement park ride called The Crazy Dance.
Unfortunately, she, Junior, and their parents get into a food fight with Mr. Peabody, the new school principal at a pizza restaurant and were kicked out and banned from going back there by the restaurant manager. Afterward, they apologize to each other and become friends while accepting each other's parents. Junior then tells Trixie about Lawanda, his dad's fiancee, and she ruins the wedding by using a bulldozer with the Caring Love Rock and having it roll down the aisle, trapping Lawanda underneath it. She is last seen walking away with Junior, Ben, and her mother.
Trixie does not appear in the sequel Problem Child 3: Junior in Love. It is not known what happened to her between both films, but it is possible that her mother broke up with Ben by that film's point since, in that movie, the latter is seen dating a therapist and the ex-girlfriend of Scoutmaster Phlim named Sarah Gray.