Best Grampa Simpson Lines

“I’ll be deep in the cold, cold ground before I recognize Missourah!”

"Something like:

“To whom it may concern, there are too many states. Please eliminate three.”

PS I am not a crackpot.

Big deal! When I was a pup, we got spanked by Presidents till the cows came home. Grover Cleveland spanked me on two nonconsecutive occasions.

From “Treehouse of Horror VI”

Lisa: Bart! Don’t you realize what this means? The next time we fall asleep, we could [weakly] die!
Abe: Ehh, welcome to my world! [falls asleep]

You guys have named most of the good ones but:

Cut to Grampa and Homer on a long car ride with Grampa obviously talking Homer’s ear off:

Grampa: Now that’s whats wrong with your generation. Now as for Bart’s generation…

When Bart fails to recognize the Wright Brother’s plane at the air show.

“That’s the Wright Brothers’ plane. At Kitty Hawk in 1903, Charles Lindbergh flew it fifteen miles on a thimbleful of corn oil. Singlehandedly won us the Civil War, it did.”

His suggestion as to how Apu can avoid being deported…

“The government can’t control the sky! What if you lived in a balloon?”

Stupid buzzards! I ain’t dead yet!

I’m thirsty! Ew, what smells like mustard? There sure are a lot of ugly people in your neighborhood. Oooh! Look at that one! Ow, my glaucoma just got worse. The president is a Demmycrat!

Don’t try to climb up [mountain] or you’ll die just like I did?!