''We've changed a multibillion-dollar corporation's business practices!'' crows Morgan Spurlock. The director of Super Size Me is relishing the news that McDonald's is kicking supersizing to the curb. His documentary, about the havoc wreaked on his body by a strict 30-day McDiet, isn't out until spring, and a McSpokesperson denies any influence on their elimination of 42-ounce Cokes and half-pound troughs of fries. Meanwhile, Spurlock (above, at Sundance) held court at Aspen's U.S. Comedy Arts Festival, where lines snaked the block for a Super Size screening. ''I applaud McDonald's in doing this,'' he says via cell phone. ''I still think they have a long way -- Pauly, it was great meetin' you, brother! -- that was Pauly Shore. He was just like, 'Yo, supersize it up, Morgan!'''