The term 'Simpson Girl' refers to Lisa Simpson, a fictional character from the long-running animated television series The Simpsons. She is the middle child of the Simpson family and is voiced by Yeardley Smith. Lisa is an 8-year-old girl who is highly intelligent and musically talented. She is an environmentalist and vegetarian, and often speaks out against the ignorance of adults. Lisa is also known for her strong moral compass and her passion for justice.