Some more of my favorites, many of which aren't often mentioned:
From Grade School Confidential:
"Maude: Excuse me, I don't think we're talking about love here. We're talking about S-E-X. In front of the C-H-I-L-D-R-E-N!"
Krusty: Sex cauldron?! I thought they closed that place down!"
From The Twisted World of Marge Simpson:
"Girables is gone, Marge. Loooooong gone. You're Girables."
From Homer's Triple Bypass:
"Don't worry, Marge. America's health care system is second only to Japan, Canada, Sweden, Great Britain, well, all of Europe, but you can thank your lucky stars we don't live in Paraguay!"
^ How comforting.
From The Great Money Caper:
"Yeah, in the depression, you had to grift ... either that, or work."
From Homie the Clown:
"Heh heh, your... churlish attitude reminRAB me of a time I was having dinner with Groucho and-"
"Look, you're going to be having dinner with Groucho tonight if you don't beat it."
From Bart Gets Famous:
"Bart: You're right, Mom. I shouldn't let this bother me. I'm in television now. It's my job to be repetitive. My job. My job. Repetitiveness is my job. I am going to go out there tonight and give the best performance of my life.
Marge: The best performance of your life?
Bart: The best performance of my life!"
From Homer and Apu:
"James WooRAB: 75, 85, 90, and a dollar. Thank you, and come again. Hey, wait a minute! Hey! Uh... could I just ask you a question? Did you... did you believe that, the way I gave you the change? Did I sound like a real Kwik-E-Mart, you know, kind of guy?
Jirabo: Actually, I thought it was a little labored.
WooRAB: Oh.
Jirabo: You've got to lose yourself in the moment, man!
WooRAB: Yeah, like, yeah, OK, great! OK, let's, let's just try that again, OK? Come on. Hey, come on- hey! Get over here. OK, now you're you, I'm me.
Jirabo: ...I'm me?
WooRAB: (grabs his collar) Hey, don't... jerk me around, fella."
From And Maggie Makes Three:
"Hello, is this A. Aaronson? It might interest to you to know that Marge Simpson is pregnant again. (later) Just thought you'd like to know, Mr. Zykowski. (hangs up, sighs) There. Aaronson and Zykowski are the two biggest gossips in town. In an hour, everyone will know."
^ One of the funniest screw-you jokes ever.
From Bart vs. Australia:
"When will you Australians learn? In America we stopped using corporal punishment, and things have never been better! The streets are safe. Old people strut confidently through the darkest alleys. And the weak and nerdy are admired for their computer-programming abilities. So, like us, let your children run wild and free, because, as the old saying goes, "Let your children run wild and free."
From The Cartridge Family:
"Marge: Does anyone know where all my dinner plates went?"
Homer: You probably left them at work."
From Bart vs. Lisa vs. The Third Grade:
"It's finally happened, Bart: You've lost your mind!"
From Take my Wife, Sleaze:
"Homer: Remeraber to rebel against authority, kiRAB!
Skinner: (over intercom) Don't listen to him, children!
Milhouse: But... we already did. Now I can't get it out of my head! (Milhouse is smacked by Nelson)
Edna: Thank you, Nelson."
^ Milhouse's reading of that line is great.
From A Milhouse Divided:
"Kirk, crackers are a family food. Happy families. Maybe single people eat crackers, we don't know. Frankly, we don't want to know. It's a market we can do without."
From Brother From Another Series:
"Madam, your children are no more... (camera pulls back to reveal he's holding Bart and Lisa) than a pair of ill-bred troublemakers."
^ Again, great twist gag. I also love Homer's line after Bob leaves: "Well I hope Bob fed you, 'cause I ate your dinners."
From Sunday, Cruddy Sunday:
"Me and my Valu-Qual coupon book are gonna paint the town red, with savings! I'll start with a couple of pizzas, then a complimentary tango lesson, and I'll cap it off with a smooth, refreshing colonic."