Jerry Seinfeld returns to Thursday night network comedy for at least one episode of “30 Rock” (7:30 p.m., NBC).

The Emmy award-winning “Rock” makes the most of its show-within-a-show story to make many self-deprecating jokes about the decline of network television since the departure of “Seinfeld” in 1998.

Seinfeld, playing himself (naturally), is dragged from a pleasant vacation when he discovers that scheming network chief Jack (Alec Baldwin) has used digital technology to insert Seinfeld into every NBC series. The fabulously wealthy comedian returns to the halls of NBC to discover the cast of “The Girly Show” in complete disarray. Liz is in denial about her breakup, Tracy has split from his wife, and Jenna has returned from a Broadway stint in the musical version of “Mystic Pizza,” a creative sojourn that added 30 pounds to her girth. “What’s happened to this network?” Seinfeld asks in an exasperated tone that works on so many levels.

In addition to Seinfeld, “Sopranos” star Edie Falco will appear later in the season on three episodes of “Rock.”

¢ One of the major changes to NBC since the end of “Seinfeld” is the emergence of NBC-Universal, extending the reach of the network’s resources with the addition of Bravo, USA and Sci Fi. The distinctions between network and cable continue to blur. Original episodes of “Law & Order: Criminal Intent” (9 p.m., USA) now move to cable. Alicia Witt will join the cast while Julianne Nicholson is on maternity leave. Look for guest spots from Steve Guttenberg, Michael Cerveris and Michael O’Keefe.

¢ Cultural anthropology meets extreme fighting on “Last One Standing” (8 p.m., Discovery), a new series that sends six top athletes to far-flung corners of the globe to compete in exotic tribal rites and traditional games that come very close to combat.

The competitors – three Americans and three Britons – will immerse themselves in tribal culture and live among their opponents before trying to survive Zulu stick-fighting tournaments in South Africa, long-distance races with the Tarahumara Indians in Mexico and matches with Brazil’s Kalapalo wrestlers. The six “stars” have made their names in wrestling, strongman competitions and BMX biking, but can they survive endurance canoeing in Papua, New Guinea?

¢ Science marks the 50th anniversary of the launch of Sputnik 1 and the beginning of the space race with three hours of space-themed programming starting at 7 p.m.

Tonight’s other highlights

¢ The warden (Craig T. Nelson) asks Earl to settle gang disputes on “My Name is Earl” (7 p.m., NBC).

¢ Worries about the security detail on “Ugly Betty” (7 p.m., ABC).

¢ Craftsman Carter Oosterhouse tackles tough renovations on “Carter Can” (7:30 p.m., HGTV).

¢ Angela continues to grieve Sprinkles on “The Office” (8 p.m., NBC).

¢ Life stops for a go-kart buff on “CSI” (8 p.m., CBS).

¢ Diahann Carroll and Ben Vereen guest star on “Grey’s Anatomy” (8 p.m., ABC).

¢ A father and daughter vanish on “Without a Trace” (9 p.m., CBS).

¢ Dr. Morretti (Stanley Tucci) continues to alienate the staff on “ER” (9 p.m., NBC).

¢ James decides his marriage is worth saving on “Big Shots” (9 p.m., ABC).

¢ On what might be the most over-the-top episode of “Mad Men” (9 p.m., AMC) yet, Betty confronts a stimulating new writing assignment while Don’s wife develops a passion for household appliances.

Cult choice

Angela Bassett stars in the 1993 Tina Turner biography “What’s Love Got to Do With It” (9 p.m., Lifetime), co-starring Laurence Fishburne as Ike Turner.