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.

Jennifer Aniston to Guest Star on 30Rock

Wheee! She's coming back to NBC's Thursday block...even for one night only!

Jennifer Aniston is guest starring on Tina Fey's 30 Rock. Last year, David Schwimmer was also a guest on this show, playing the eco-mascot Greenzo (Watch the Video).

The actress is said to be already filming her scenes.

30 Rock is the last show to premiere this fall, coming back to TV on October 30th.