Monica Geller is a little bit crazy, but definitely seems to be the leader of the group of Friends.  She's Ross's sister and high school best friends with Rachel and kind of ties to the group together as a mother-like character.

Monica is known for being a little OCD and for being overweight in high school.  Now?  She's a bit of a chef but holds various jobs during the season.

At the end, Monica ends up marrying Chandler in season seven.

Monica Geller Quotes

Monica: Hey, Joey! What would you do if you were omnipotent?
Joey: Probably kill myself.
Monica: Excuse me?
Joey: Hey, if Little Joey's dead, I got no reason to live.
Ross: Uh Joey... omnipotent.
Joey: You are? I'm so sorry. (To Chandler) I didn't know, I thought it was one of those theoretical questions.

Monica: What's "PLEH?"
Joey: That's help spelled backwards so that the helicopters can read it from the air!
Monica: Ah...what's doofus spelled backwards?

Friends Quotes

Joey: (Wearing an old-looking hat) Hey.
Monica: Hey.
Rachel: Hey. Well, look at you, finally got that time machine working, huh?
Joey: Seriously, you like it? This guy was selling them on 8th avenue and I looked at them and I though, you know what I don't have?
Monica: A mirror?
Joey: Fine, make fun. I think it's jaunty.

Monica: What's "PLEH?"
Joey: That's help spelled backwards so that the helicopters can read it from the air!
Monica: Ah...what's doofus spelled backwards?