Abe Simpson: “Your dad used to be smart as a monkey, but then his mind started gettin’ lazy, and now he’s dumb as a chimp”
I’ve been trying to get back to the monkey state the past week. No success so far.
Legs: Johnny Tightlips, where’d they hit ya?
Johnny Tightlips: I ain’t sayin’ nothin’.
Legs: But what’ll I tell the doctor?
Johnny Tightlips: Tell him to suck a lemon.
Oh, Lisa, you and your stories: Bart’s a vampire, beer kills brain cells. Now let’s go back to that…building…thingie… where our beds and TV… is.
Oh, yeah, what are you gonna do? Release the dogs? Or the bees? Or the dogs with bees in their mouth and when they bark, they shoot bees at you?
Homer: But Marge! I was a political prisoner!
Marge: How were you a political prisoner?!
Homer: I kicked a giant mouse in the butt! Do I have to draw you a picture?
Okay, brain. You don’t like me, and I don’t like you, but let’s get through this thing and then I can continue killing you with beer.
Old man: Take this doll, but beware; it carries a terrible curse.
Homer: Ooo, that’s bad.
Old man: But it comes with a free serving of frozen yoghurt!
Homer: That’s good!
Old man: The frozen yoghurt is also cursed.
Homer: That’s bad.
Old man: But it comes with your choice of toppings!
Homer: That’s good!
Old man: The toppings contain potassium benzoate…
Homer: (confused look)
Old man: That’s bad.
Homer: Can I go now?
You left out “It’ll happen to you!”, which makes it for me.
My absolute favourite is from Lisa the vegetarian:
“(Lisa) “I’m going to become a vegetarian”
(Homer) “Does that mean you’re not going to eat any pork?”
“Yes”
“Bacon?”
“Yes Dad”
" Ham?"
“Dad all those meats come from the same animal”
“Right Lisa, some wonderful, magical animal!””
Marge: Homie, maybe we should go inside.
Homer: But, Marge, that little guy hasn’t done anything yet. Look at him. He’s going to do something and you know it’s going to be good.
[Marge pulls him back into the house and shuts the door]
[loud ninja yell and thump]
Homer: Aw…
Grandpa had the best line…
“I used to be with it. But then they changed what ‘it’ was.’ Now what I am with, is no longer ‘it.’ And what is ‘it,’ seems just weird and scary.”
Marge: C’mon, Homer, Japan will be fun. You like Rashomon.
Homer: That’s not how I remember it.
“I for one welcome our new insect overlords…” (Kent Brockman)
“I’ve had enough of your Vassar bashing, young lady.” (Homer to Lisa)
(After Mr. Burns asks him if he found the bathroom) “Uh, yeah…” (Homer)
And my favorite: “Oh Lord, bless this rocket house and all who dwell within this rocket house.” (Homer)
I’ve got powers… Political powers!
Oh, I forgot:
Chief Wiggum: “You know you’re not supposed to go in there. What is your fascination with my forbidden closet of mystery?”
Chief Wiggum: Well, I hope you’re happy, Simpson. Those prisoners were one day away from being completely rehabilitated.
Wiggum: Okay, I assume you all know why you’re here. [ducks as chair thrown at him] That’s right, you’re all angry, sick people. But, over these next eight hours, you will be broken down to the level of infants, then rebuilt as functional members of society, then broken down again, then lunch, then, if there’s time, rebuilt once more.
Wiggum: And as if that wasn’t enough, we have a special guest – why, it’s Curtis E. Bear, the courtesy bear. For the next three hours, this bear will take your verbal and physical abuse with good nature and aplomb. So, if you’ll all just grab one of these two-by-fours…
Eddie: Um, Chief? Can I at least shield my crotch?
Wiggum: Bears can’t talk, Eddie.
Announcer: Your cable television is experiencing difficulties. Please do not panic. Resist the temptation to read or talk to loved ones. Do not attempt sexual relations, as years of TV radiation have left your genitals withered and useless."
Wiggum (checking): Well I’ll be damned.
From “Homer at the Bat”
Hyponotist: You will give 110 percent.
Team (hypnotized and in unison): That’s impossible. No one can give more than 100 percent. By definition, that is the most anyone can give.
In on episode Marge and the kids have moved out:
Homer “there’s no one there to hear my various witty remarks.”
Apu: I have come to make amends, sir. At first, I blamed you for squealing, but then I realized, it was I who wronged you. So I have come to work off my debt. I am at your service.
Homer: You’re… selling what, now?
Apu: I am selling only the concept of karmic realignment.
Homer: You can’t sell that! Karma can only be portioned out by the cosmos.
[Slams the door]
Apu: He’s got me there.
Ninja’d in Post #57. 
Mentioning Simpsons quotes without a paddlin’? You better believe that’s a paddlin’.
This has purple stuff inside it. Purple is a fruit.
Bob: You wanted to be Krusty’s sidekick since you were five! What
about the buffoon lessons, the four years at clown college.
Cecil: I’ll thank you not to refer to Princeton that way.
One you hear a lot at McGill:
Marge: Oh Lisa, you can always go to McGill! It’s the Harvard of Canada!
Lisa: Anything that is the something of something, isn’t really the anything of anything.
Skinner: Mmmm, Brown. Heckuva school. Weren’t you at Brown, Otto?
Otto: Yup. Almost got tenure, too.
Titanya: “But Duff Man, you said if I slept with you I wouldn’t have to touch the drunk!”
Duff Man: “Duff Man… says a lot of things! Oh, yeah!”
“The Aurora Borealis? At this time of year? At this time of day? In this part of the country? Localized entirely within your kitchen?”
“Yes.”
“May I see it?”
“…No.”