Robert Stack, the former star of “The...

Robert Stack, the former star of “The Untouchables,� “Name of the Game� and “Most Wanted,� has joined the cast of CBS’ “Falcon Crest.� He’ll begin appearing in February, playing what the producers describe as “an extremely powerful industrialist with an unsavory past.�

ABC correspondent Richard Threlkeld will anchor “Diagnosis: Malpractice,� an hourlong documentary that the network plans to broadcast Dec. 27. ABC says the program “is the result of a six-month investigation into the causes and effects of this country’s malpractice dilemma.� It looks at some major cases filed against doctors and also reports on physicians’ claims that lawyers bear the responsibility for making malpractice a national crisis.

Melissa Gilbert, former child star on “Little House on the Prairie,� is making a big jump in “The Godfather’s Wife.� She plays a woman who marries a lawyer (Joe Penny), only to find that he’s a high-ranking member of the underworld. Also in the cast of the NBC movie are Talia Shire, Eileen Brennan and Tony Franciosa.

CBS is planning to tape the festivities surrounding the renovation of Carnegie Hall this week and will broadcast it as a special later. Scheduled to perform at “Carnegie Hall: The Grand Reopening� are Marilyn Horne, Frank Sinatra, Isaac Stern, Benita Valente and Yo-Yo Ma.

Woody Strode, Joe Seneca, Papa John Creach, Tiger Haynes and Sandman Sims are among those who aid Lou Gossett in the CBS TV movie, “A Gathering of Old Men.� Gossett plays an admitted killer, and Richard Widmark is the sheriff holding him.

“We Got It Made,� which ran for one season on NBC in 1983-84, is being revived for syndication, with Teri Copley and Tom Villard back from the original cast. The new version will premiere next fall and has been purchased by the NBC station group, which includes KNBC Channel 4 in Los Angeles.