Jennifer Aniston plays a crazy woman on 30 Rock

Last week, the buzz was Jennifer Aniston is returning to NBC via a guest stint on 30 Rock but it still wasn't clear what her role is.

Well, here's the scoop --- She's not playing herself, thankfully. She is playing a woman who will "rock Jack Donaghy's world".

My well-informed sources say Aniston plays Liz and Jenna's old roommate from Chicago, who pays them a visit in the Big Apple. She's a free spirit who loves to party and isn't opposed to sleeping around. In fact, a certain slick, Republican 30 Rocker will catch her eye.

Word is, their "relationship" won't be the healthiest, as Donaghy gets addicted to Aniston's character, and she becomes a total psycho... much to poor Liz Lemon's disapproving chagrin. | Korbi

Crazy Jen? That I want to see!

30 Rock premieres its third season on October 30th.