Agnes Skinner is Principal Seymor Skinner's very controlling elderly mother.  Agnes was actually revealed to have adopted Seymour during "The Principal and the Pauper."  Agnes also often serves as a friend of Marge in many adventures.

Agnes Skinner Quotes

Principle Skinner: Oh, licking envelopes can be fun! All you have to do is make a game of it.
Bart: What kind of game?
Principle Skinner: Well, for example, you could see how many you could lick in an hour, then try to break that record.
Bart: Sounds like a pretty crappy game to me.
Principle Skinner: Yes, well... Get started.

I was in love with a soldier boy on leave from Korea. It was a fifties style of romance, five minutes of sex and a lifetime of regret. He went back to his war and I went back to my dream of pole vaulting in the Helsinki Olympics. But there was a bump in the road, a bump named Seymore.

Agnes [in flashback]

The Simpsons Quotes

Wow, now I see why they call you Miss Hoover. You must have been vacuuming for an hour.


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!