Abraham "Abe" Simpson is Homer's fatherly and commonly just referred to as grandpa on the show.  Despite being a decorate war veteran with some of the most impressive stories, Grandpa is commonly regarded as a loon and his stories considering rambling by the family.

Grampa Simpson Quotes

You know, you remind me of a poem I can't remember, and a song that may never have existed, and a place I'm not sure I've ever been to.

Grampa

Grandpa: That's how I got my idea for a suitcase with wheels: from a commercial for a suitcase with wheels.

The Simpsons Quotes

Homer: (Wearing glasses) The sum of the square roots of any two sides of an isosceles triangle is equal to the square root of the remaining side!
Man: (From inside a bathroom stall.) That's a right triangle, you idiot!
Homer: D'oh!

You know, you remind me of a poem I can't remember, and a song that may never have existed, and a place I'm not sure I've ever been to.

Grampa