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

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]

Agnes: Where did you learn to sweep like that?
Marge: I've been training all my life. I once swept red wine off a white carpet.

The Simpsons Quotes

(Bart shows the whole classroom the tape for his project called, "How Kittens Are Born: The Ugly Truth")
Bart: and here comes Snowball II. This is the one we kept.
All: EWW!!
Bart: We were gonna keep the gray one, but the mother ate her.
All: EWWWWW!!
Martin: Mrs. Krabappel, he's traumatizing the children!
Mrs. Krabappel: As usual, I agree with you, Martin. Bart, shut that off and take your seat immediately!
Bart: Oh, look! This is really cool. When I hit reverse, I can make 'em go back in.
(The whole classroom screams)

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!