Lisa the Vegetarian--so many great lines:
Lisa: Dad! Can't you have some other type of party, one where you don't serve meat?
Homer: All normal people love meat. If I went to a barbeque and there was no meat, I would say 'Yo Goober! Where's the meat?'. I'm trying to impress people here, Lisa. You don't win friends with salad.
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Homer: I understand honey. I used to believe in things when I was a kid.
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Homer: Are you saying you're never going to eat any animal again? What about bacon?
Lisa: No.
Homer: Ham?
Lisa: No.
Homer: Pork chops?
Lisa: Dad, those all come from the same animal.
Homer: Heh heh heh. Ooh, yeah, right, Lisa. A wonderful, magical animal.
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Principal Skinner: Uh oh. Two independent thought alarms in one day. The students are overstimulated. Willie! Remove all the colored chalk from the classrooms.
Groundskeeper Willie: I warned ya! Didn't I warn ya? That colored chalk was forged by Lucifer himself.