BY DAVID KRONKE >TV CRITIC

A strange and distressing thing has happened to NBC during "30 Rock's" tenure on its airwaves. When it debuted, it was one of the network's least-watched (if most-acclaimed) shows, drawing 5 million, 6 million, maybe 7 million viewers.

We'll soon see how it does as the show enters its third season, having recently won its second Outstanding Comedy Series Emmy and stoked by the heat of show creator Tina Fey's beloved impressions of Sarah Palin.

But even if it doesn't budge from its earlier numbers, no big deal - most NBC shows these days draw such low ratings numbers.

As "30 Rock" commences season three, Liz Lemon (Fey) is determined to adopt a baby, while Jack (the hilariously seething series MVP Alec Baldwin) has returned from his ignominious time in Washington to try to get his job back from Devon Banks (Will Arnett), about whom he kvetches, "He's a party boy with a grown man's job" (a not-so-shadowy reference to NBC Entertainment co-chairman Ben Silverman, reinforced by Banks' propensity for blowing off meetings).

Meanwhile, Jenna (Jane Krakowski) is feeling slighted because she hasn't been paid for her participation in Tracy's (Tracy Morgan) wildly popular video game, which he calls "the most profitable thing since the war on terror." So when the uptight and inappropriate representative from Liz's adoption agency (Megan Mullally) shows up to take in the conditions of Liz's workplace, the only possible outcome is disaster.

Next week, Oprah Winfrey appears as herself - well, sort of - as Liz meets her on a plane and falls apart. Meanwhile, Jack must deal with a disgruntled Olympic tetherball athlete: "We staged several events so that Americans would win more medals," Jack explains; one of the losers is threatening to go public.

Kenneth the Page (Jack McBrayer) is scandalized: "Was any of it real?" he asks, distraught, of NBC's Olympics coverage. "Beer pong, Jazzercize, women's soccer?" Jack is forced to teach the upright Kenneth a lesson in situational ethics.

"30 Rock" remains a giddily entertaining show - cartoonish and outsize one moment, bracingly and witheringly smart the next. There are withering inside jokes for those who understand the TV industry and broadly silly gags for those who don't.

And as NBC's fortunes continue to wane, it's at this point the network's grandest achievement, engaging in self-mockery even as the once-proud peacock sheds the feathers in its cap.

David Kronke, (818) 713-3638 david.kronke@dailynews.com