Along the same vein as the “spelling Yale with a 6” line:
Patty (or Selma?): “He (Otto) got all the questions wrong, and misspelled ‘bus’ on the application.”
Homer the Vigilante: “Oh, you can use statistics to prove anything! 41% of all people know that.”
Kent Brockman: What do you say about the accusations that your group causes more crimes than it prevents?
Homer: Oh Kent, I’d be lying if I said my group didn’t commit crimes.
Kent:…touche.
Marge: Come on, Homer. Japan will be fun. You liked Rashomon.
Homer: That’s not how I remember it.
Homer: In this house, we obey the laws of thermodynamics!
(The 2nd one is quite handy.)
Abe: The metric system is the tool of the devil! My car gets forty rods to the hogshead and that’s the way I likes it.
Homer: But…the ball! His groin! Ah ha! It works on so many levels!
Hans: I was saying “Boo-urns”
(Yeah, my favorite ep is “A Star is Burns”. What of it? 
)
BURNS: Smithers, I’m starving!
SMITHERS: I could send out for some Chinese…
BURNS: BAH! Those people are all gristle!
Astronaut: There’s no air in space,.
Homer: There’s an air and space museum
Jasper: Who shot who in the what now?
Smithers: “Smithers : I’m afraid we have a bad image, sir. Market research shows people see you as something of an ogre.”
Burns: “I ought to club them and eat their bones!”
Burns: “I’ll be brief. Family, religion, friends. These are the three demons you must slay if you wish to succeed in business.”
Lisa: “You don’t understand!”
Homer: “Just because I don’t care doesn’t mean I don’t understand.”
Homer: “I used to Rock and Roll al night, and party every day. Then it was every other day. Now I’m luck if I can a half an hour a week in which to get funky”
Otto: "Why do they call them ‘fingers’, I’ve never seen 'em fing.
oh, there they go."
“I’m normally not a praying man, but if you’re up there, please save me Superman!”
“Call me back, Ishmael.”
Homer: “Oooh, I’m making people happy! I’m the magical man, from Happyland! I live in a gumdrop house on lollipop lane!”
(shuts door closed)
(reopens door)
“By the way, I was being sarcastic!”
(closes door again)
Marge: “Well duh!”
Let the fools have their tartar sauce.
YOU! Conceal it.
Homer driving car hits a deer…
Homer: D’oh
Lisa: A deer
Marge: A female deer
“Is there no place in this world for a man with a hundred and five IQ?”
Reading Digest Essay Contest: Brevity is…wit.
Homer hallucinating after eathing all those hot peppers:
“Ha-HA! Ha-HA!”
“I can’t tell where Lenny ends and Carl begins.”
“Statements like that are why people think we’re gay.”
“I’ll have some taquitos.”
Ah, that’s true. It’s been a while.
Lurleen Lumpkin: Oh, Homer, you’re as smart as you are handsome!
Homer: Hey! Oh, you meant that as a compliment…
Homer: That’s it! You people have held me back long enough! I’m going to clown college!
Bart: I don’t think any of us expected him to say that.
Ohhhh…why won’t those stupid idiots let me into their crappy club for jerks?