Lisa Marie Simpson. Lisa is an extremely intelligent girl, with an I.Q. of 159 or so. She plays the Saxophone. Many fans of the show claims that Lisa's birthday is September 28, although in "My Sister, My Sitter," we learn that Lisa is 2 years and 38 days younger than Bart, which would put her birthday on May 9, 1981. Lisa is also a Buddhist, and a vegetarian much to her fathers dismay. Lisa is the most intelligent person in the school and in one of the episodes she was the only person in the school's history to graduate.