Lisa Marie Simpson, voiced by Yeardley Smith, is Homer and Marge's oldest duaghter and the middle child on The Simpsons.  Lisa is very intelligent, plays the saxophone, is a vegetarian, Buddhist, and definitely a bit of a young political activist.  She's basically the complete opposite of her brother, Bart.

Lisa Simpson Quotes

(Lisa tries to teach Bart a method to clear his mind of distraction.)
Lisa: Bart, I have a riddle for you. What's the sound of one hand clapping?
Bart: Piece of cake.
(Bart opens and closes his right fist quickly, making a sound.)
Lisa: No, Bart. It's a 3000-year-old riddle with no answer. It's supposed to clear your mind of conscious thought.
Bart: No answer? Lisa, listen up.
(Bart quickly opens and closes his fist again.)

Lincoln, Lincoln. I've been thinkin'. What the hell have you've been drinkin'? Is it water? Is it wine? Oh, my gosh. It's turpentine!

Bart & Lisa

The Simpsons Quotes

Homer: (Wearing glasses) The sum of the square roots of any two sides of an isosceles triangle is equal to the square root of the remaining side!
Man: (From inside a bathroom stall.) That's a right triangle, you idiot!
Homer: D'oh!

Mr. Burns: Oh, and one more thing: you must find the jade monkey before the next full moon.
Smithers Actually sir, we found the jade monkey. It was in your glove compartment.
Mr. Burns: And the road maps, and ice scraper?
Smithers: They were in there too, sir.
Mr. Burns: Excellent! It's all falling into place...