"Saturday Night Live" star Tina Fey is reaching into the roster of the late-night comedy to cast her new, semi-autobiographical sitcom.

Rachel Dratch, an "SNL" regular, is the latest to join the cast of Fey's yet-to-be-titled pilot about the head writer on a variety show.

The pilot for NBC is slated to be filmed in early spring and, if it is picked up by the network, will be based in New York.

Fey, who is writing and executive producing the show, will keep her job as head writer at "Saturday Night Live" and "Weekend Update" anchor.

But, sources say, it has been hard for NBC to work around the women's grueling work schedule -- including Fey's duties as a new mom.

Tracy Morgan, another "SNL" alum, is expected to join the cast of the new half-hour comedy, which is under serious consideration for NBC's fall schedule.

Production of the show would be tricky, since Fey's scenes would have to filmed while she is on hiatus from "SNL" and banked for future airing.

On the proposed series, Fey's character is beset with the hassles of being the peacemaker between the show-within-a-show's fickle star and its executive producer.

At the same time, NBC is developing a high-profile drama also loosely based on "SNL" by "The West Wing" creator/writer Aaron Sorkin.

That show about the behind-the-scenes action at a fictional late-night network sketch comedy show is tentatively titled "Studio 60 on the Sunset Strip."

It features a powerhouse cast, including Matthew Perry, Amanda Peet, Steven Weber, D.L. Hughley and Evan Handler ("Sex and the City"), Michael Stuhlbarg, Nathan Corddry ("The Daily Show") and Carlos Jacott.

Despite having two shows with similar themes in the works, it is very possible that both shows could be on NBC's fall schedule, insiders says.

The network is lagging in third place behind CBS and ABC in total viewers and is trying ideas it might not have attempted a few years ago when it was on top of the Nielsen charts.

"One is a 60-minute drama and one is a 30-minute comedy," says an industry source familiar with both shows. "Look at it this way, 'ER' and 'Scrubs' have co-existed quite nicely on the [NBC] schedule for many years."