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: How can you people turn on snakes after all they've done for you?
Grampa: I'm an old man, I hate everything but Matlock. Ooh, it's on now.

Lisa: Dad, I think he's an ivory dealer! His boots are ivory, his hat is ivory, and I'm pretty sure that check is ivory.
Homer: Lisa, a guy who's got lots of ivory is less likely to hurt Stampy than a guy whose ivory supplies are low.

The Simpsons Quotes

Homer: You're welcome to watch anything you want on TV.
Bart: TV Sucks.
Homer: I know you're upset right now so I'll pretend you didn't say that!

(to Lisa) Seymour Skinner never puts all his eggs in one basket. That's why they call me "Two Basket Skinner." (pause) What? They do.

Principal Skinner