Karen Kramer, widow of director Stanley Kramer, is mad, mad, mad, mad over comparisons being made between Jerry Zucker's current "Rat Race" and her late husband's 1963 seminal all-star comedy, "It's a Mad, Mad, Mad, Mad, World." The Los Angeles Times reports that not only is Karen guardian of the legacy of her late husband (who died at age 87 this past February), but she is peddling her own sequel of the movie to MGM/UA -- with several of the original stars attached. "The sad truth is that Mr. Zucker tried to build a better mousetrap and failed -- exploiting a brilliant classic that was the daddy of its kind to create an inferior, unauthorized imitation," she told the Times, calling this "a case of artist's rights." Exacerbating the situation, Zucker knocked "Mad World" in a Times interview last week, saying that in his movie, "The humor comes out of the story and acting, as opposed to saying, 'OK, now it's time for Buddy Hackett to do his shtick.' " That caused some of the original "Mad" stars to lash out at Zucker, too. (Along with Hackett, "Mad World" also starred Jonathan Winters, Milton Berle, Mickey Rooney, Sid Caesar, Edie Adams and the late Ethel Merman in her best screen role.) Sid Caesar, 78, said, "That movie was a cut above the comedy today, which is all about cursing and sex. Far from being 'shtick,' it was rooted in character -- not a bunch of jokes strung together." Added Edie Adams, 71: "Those of us who have been in the business a year or two longer than Zucker know that most comics are great actors and very few great actors can do comedy. Perhaps he should have done a remake of (Zucker's own) 'Airplane!' and put a whoopee cushion on each seat." Commented a contrite Zucker, 51: "I apologize 1,000 times for my statement."