Charles Montgomery Burns, usually just known as Mr. Burns, is the owner of Springfield Nuclear Power Plant and therefore the boss of Homer.  Mr. Burns is pure evil and most jokes are related to his age and his constant references to the past due to the fact the guy is over 100.

Mr. Burns Quotes

Mr. Burns: (reading Homer's letter) "Dear Mr. Burns. I'm so glad you enjoyed my son's blood, and your card was just great." Why Simpson, you've made my day, you're a true gentlemen.
Homer: Well I-
Mr. Burns: Hello, there's more. (continues reading) "In case you can't tell, I'm being sarcastic. You stink! You are a senile bucktoothed old mummy with bony girl arms and you smell like an elephant's butt!"

Homer: That is the most amazing doughnut I've ever tasted
Mr. Burns: Well, if you stay on with the Springfield nuclear plant, you could have one of these tasty beauties every day.
Lenny [about doughnut]: One of these every day might kill us.
Carl: Can we get a health plan to go with them?
Mr. Burns: Sure, you could have a health care or.... two donuts a day.

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