Peggy Olson has succeeded, professionally, in a man's world.
She's a junior copywriter at Sterling Cooper and has shown little remorse for the child she never cared for; her family takes care of the son she had with Pete.
Peggy hails from Brooklyn and is sort of Don's protege. He woos her into his new company at the conclusion of season three.
Peggy: This is supposed about my job, not the meaning of life.
Don: So you think those things are unrelated?
Peggy: I didn't know you'd be in a mood.
Don: Do you want to do this or not?
Peggy: Why don't you just write down all your dreams so I can shit on them?
You'll have to believe me that I'll forget this. I don't want you treating me badly because I remind you of it.Peggy