Lisa is 8 years old; according to her brother Bart, Lisa is 2 years and 38 days younger than him. This presumably places her birthday as being on May 9, given Bart's birthday is April 1. While she was shown as being born during the 1984 Summer Olympics in one flashback episode ("Lisa's First Word"), given that the characters in The Simpsons generally don't age, no specific year for her birth can truly be given (besides "always" being born "about 8 years ago").
Lisa is an extremely bright girl, with an IQ of 159. Officially, her highest grade is an A+++ which she earned by cheating on a test on The Wind in the Willows. (She later re-marked the test as an F.) Once, when she was unable to attend school due to a teachers' strike, she suffered a sort of "school withdrawal" and invented a perpetual motion machine; Homer chastised her for this, telling her that in the Simpson household "we obey the laws of thermodynamics!"
Her musical abilities are extensive: she sings with a powerful voice, and has been seen playing both the acoustic six-string and electric bass guitar proficiently. However, her great love is jazz blues performed on her baritone saxophone, (much like the one used by Gerry Mulligan). She uses a 4 & 1/2 reed, a fairly stiff reed for an 8 year old. Her musical inclinations were greatly nourished through her relationship with the late jazz musician Bleeding Gums Murphy. She is also fluent in Swedish (though it is unknown whether she actually can as this was only revealed in Treehouse of Horror) and French, and understands Chinese as seen from listening to Yao Ming.
For all of, or because of, her talents, her character was gradually remodeled as an outcast whose intelligence and principles the other children, and many adults, cannot appreciate.
Coupled with her intelligence is a strong sense of leftist political and social conviction she is ever ready to advance. For example, Lisa is an ovo-lacto vegetarian (she has stated she plans on becoming a vegan) and a practicing Theravada Buddhist, although she pays lip service to her family's Christian denomination. In addition, she is a supporter of the Free Tibet movement and the anti-apartheid campaign. She has also revealed to be a wiccan in one episode. She also has a strong skepticism against the supernatural, applying Occam's Razor when the rest of the family fails to. Her skepticism in the supernatural is further shown by her disbelieving in a so-called angel when the whole town believes that the specimen in question is in fact an angel, stubbornly seeking out scientific disproof of this "Angel" from Stephen Jay Gould (which she eventually finds although the hoax's startling climax momentarily fools her). She is seen by some to whine at times or to have a persistent sense of superiority that often grows into self-aggrandizement, but she retains a childlike impressionability despite her intelligence, for example, she would love to have a pony and enjoys her mother's homemade waffles (and is disappointed when they turn out to be square pancakes). She has solved various problems around Springfield, often in tandem with her brother Bart.
Lisa's future has been revealed in three episodes, by a fortune teller in a medieval carnival, by a Native American who is in charge of an Indian casino and by Professor Frink. In the episode "Lisa's Wedding", the fortune teller reveals that Lisa will fall in love with a British man who matches her intellectually, but her marriage will be cancelled because of a dispute over his dislike for the Simpson household. It is also hinted at that Lisa will lose her virginity to Milhouse. In the episode "Bart to the Future," the American Indian reveals that Lisa will become the "first straight female US President", having defeated Chastity Bono. A balding middle-aged Milhouse van Houten works for the Lisa Simpson Administration. Her administration's main issue is the massive foreign debt. She appoints Bart as the "Secretary of Keeping it Real" as a way to keep him out of the way at Camp David. Professor Frink shows that she is to take Milhouse to her Prom.
Lisa is someone who is very eclectic in her knowledge and shows a deep understanding of the world around her. She may be seen as a child prodigy. Critics have also pointed out that the character of Lisa is a hint to the slighting of children in the real world though they may be a lot more knowledgeable and perceptive than the adults. Lisa shares her intellect and over-achieving personality with many other female members of the Simpson family (it has been revealed that male Simpsons inherit a gene that causes stupidity and under-achieving, which is carried on the Y chromosome).
Like every young girl, Lisa has also gone through periods of rebellion. For a short time, she smoked cigarettes with older girls in the school bathroom, and even told her teacher, Elizabeth Hoover, to "shove it" when she did not feel like sprinkling sparkles on her art assignment (a parody of the 1953 film The Wild One).
In Japan, the broadcasters of the series found they were able to turn the apparent viewer dislike of the series around by focusing marketing attention on Lisa. Apparently, her struggles to be a voice of reason and a force of good in her family and her city struck a chord with the Japanese.
Lisa only watches TV for The McLaughlin Group and Itchy and Scratchy. In Home Away From Homer, it is also revealed that Lisa is a fan of National Public Radio and David Sedaris. In "Milhouse of Sand and Fog" it is revealed that she enjoys watching The O.C.
Her favourite album is Miles Davis Birth of the Cool.
Her favorite food is couscous.
- Won the regional Reading Digest (a takeoff of Readers' Digest) essay contest
- Served brief term as Little Miss Springfield
- Co-invented the Lisa Lionheart doll
- All-star goalie in pee-wee hockey
- Discovered Jebediah Springfield was a murderous pirate named Hans Sprungfeld
- Helped Charles Montgomery Burns recover his fortune, which made Burns $120,000,000 with the "Li'l Lisa" recycling plant. She was offered 10% of the profit but turned down the offer, giving Homer five heart attacks: four simultaneously for giving up the "$12,000" that Homer had mistaken it to be, and another for learning the real value of the 10%.
- Passed with "satisfactory completion" of the second grade as the first female cadet at Rommelwood Military Academy
- Tree-sat a redwood
- Came second in Spellympics
- Won Li'l Starmaker singing competition
- Is a member of Mensa.
- Was co-mayor of the town along with the rest of the Springfield charter of Mensa which included Professor Frink, Dr. Hibbert, the Comic Book Guy, Seymour Skinner and Lindsey Naegle.
- Only female member of the Springfield Elementary club "The Superfriends." She is also the only member without a nickname.
- Series creator, Matt Groening claims Lisa is his favorite character, because she is the only member of the Simpsons family capable of escaping Springfield.
- Granddaughter to Abraham Simpson, Mona Simpson and Jacqueline Bouvier.
- Daughter to Homer Jay Simpson and Marjorie Bouvier Simpson.
- Younger sister to Bartholomew Jo-Jo Simpson and older sister to Margaret Simpson.
- Niece to Herbert Powell, Abbie, Patty Bouvier and Selma Bouvier Terwilliger Hutz McClure.