Bartholomew "Bart" JoJo Simpson is a character from The Simpsons, which has been both an inspiration and competitor to South Park. His first appearance was in "Cartoon Wars Part II" as he helped Cartman cancel Family Guy.
A South Park character parodying the character is seen in "Cartoon Wars Part II". He mentions historical moments from Bart's life and assisted Cartman to try to cancel Family Guy and convince FOX Network to stop airing the show. When Kyle arrives to stop Cartman, Bart knocks him out with his skateboard. After hearing one of Kyle's "gay little speeches", Bart instead decides to help save Kyle and Family Guy.
In "Cartoon Wars Part II", the character parodying Bart is portrayed as a boy with a slightly yellowish skin tone and tall, spiky blond hair. He wears a red shirt, as well as blue denim shorts and blue sneakers. Although he resembles his original character, some differences in the clothing's color scheme are still visible.
In "The Problem with a Poo", Bart had a very similar appearance to the original character, having a new body shape reminiscent of the Simpsons cartoon style. The few changes made include green shorts, red tennis shoes, and his hair appearing to be slightly combed.
On The Simpsons, Bart is usually portrayed as mischievous, rebellious, and cunning, but with a good heart. On South Park, he is portrayed similarly, but maybe somewhat worse-intentioned and destructive, as he stated that he could do terrorism. Additionally, Bart later helped Cartman with said terrorism by knocking out the good-intentioned Kyle with his skateboard, then helped keep him trapped. However, Kyle does seemingly convince him to free him so he can stop Cartman by telling him something about becoming as bad as he is, likely indicating more moral responsibility. He also seems to strongly dislike Family Guy.
- Bart is originally voiced by a female actress (Nancy Cartwright) on The Simpsons. Similarly, he is also one the of few male characters on South Park to also be voiced by a woman.
- Bart is based on Matt Groening, just like how Kyle and Stan are based on Matt Stone and Trey Parker.