If you asked Kevin Costner, he’d dispute the first part of the title of “Truth Or Dare,” the Madonna documentary. Costner, much to his surprise, makes a memorable cameo. He goes backstage to tell her how “neat” her show was, and when he leaves, she jams her fingers down her throat to simulate vomiting. Buzz hears Costner’s telling friends that he was set up. He was invited backstage, didn’t like the show, and neat was the only word he could think of. He’s steamed over being used as a joke in the pic, but gets the last laugh. Costner will soon play the bodyguard of a pop star in “Bodyguard.” Buzz hears that Madonna tried for the starring role, but was shot down for Whitney Houston.