Jennifer Aniston is making a guest appearance on 30 Rock opposite Tina Fey and Alec Baldwin, a source tells Star.

The episode is expected to film in New York next week and will air this fall.

"Jen has wanted to stay busy since her split with John Mayer because she doesn't want the world to think she's at home crying into her pillow," says the source. "She is up for any kind of work and thinks doing a big TV series is a clever way to ramp up publicity for her fall films."

The source says Jen chose 30 Rock "because she thinks it's hilarious and she is a major, major fan of Alec's."