The Simpson Kid term refers to two characters from the popular animated television series The Simpsons. Lisa Simpson is an 8-year-old girl who is the middle child of Homer and Marge Simpson. She is highly intelligent, musically talented, and a strong advocate for environmentalism and animal rights. BART Simpson is Lisa's older brother and the eldest child of Homer and Marge. He is a mischievous 10-year-old boy who often gets into trouble at school and with his family. Both Lisa and BART are beloved characters in the show and have been featured in many episodes since its debut in 1989.