Jane Lynch will be busy with her Glee duties, but Party Down has nabbed a fine replacement: Will & Grace Emmy-winner Megan Mullally.

Mullally, who’s hosted a talk show and co-starred in ABC’s sitcom In the Motherhood in her post- W&G days, will play single mom Lydia, who leaves her small town for life in Hollywood, where her teen daughter tries to become an actress while mom slings apps with the Party Down catering crew.

From the Starz press release:

Burbank, CA. – September 2, 2009 – Starz keeps the “Party” hopping and the laughs flowing with the addition of one of television and film’s most beloved comediennes, Megan Mullally, to  the cast of the crowd-pleasing original comedy series, Party Down, Starz Media EVP Originals Productions and Development Bill Hamm announced today. Production on the second season begins in mid-September in Los Angeles. The half-hour comedy about a Los Angeles catering team – Hollywood wannabes stuck working for tips while hoping for their big break – is tentatively scheduled to return to the air on Starz in April of 2010.

Mullally (Will & Grace, Fame) will play Lydia Dunfree, a middle-aged refugee from a lousy marriage who leaves small town life to move to Hollywood where her 13-year-old daughter Escapade hopes to make it as an actress. While the younger endures the audition process, her naïve and eternally optimistic mother Lydia feels honored just to be among the show business “pros” of the Party Down catering company. Her search for Mr. Right only complicates matters for Lydia, but ups the laughs on the show.

She joins a talented ensemble of actors on the comedy, labeled “a must-see” by USA Today and called “straight-up funny” by Entertainment Weekly. As the first season ended, Ron Donald (Ken Marino), the aggressively dysfunctional former leader of the Party Down Catering company, was headed off to manage a Soup N’ Crackers franchise; leaving one-time actor Henry Pollard (Adam Scott) to fill the void as leader; Roman DeBeers (Martin Starr) a self-proclaimed Sci Fi visionary, was still trying to get his screenplay noticed – by anyone; while actor, musician and all round cute guy Kyle Bradway (Ryan Hansen) landed a role in an upcoming action film; and Henry’s flame Casey (Lizzy Caplan) left him at the catered altar to do a few months of stand-up on a cruise ship.