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

Officer Eddie: (reading Steve Sax's license) Well well, Steve Sax, from New York City.
Officer Lou: I heard some guy got killed in New York City and they never solved the case. But you wouldn't know anything about that now, would you, Steve?
(Lou and Eddie laugh)
Steve Sax: But there are hundreds of unsolved murders in New York City.
Officer Lou: You don't know when to keep your mouth shut, do you, Saxxy Boy?

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

Bart