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: (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!"
Mr. Burns: I specifically said, no geeks!
Milhouse: But my mom says I'm cool...