The Post’s Michael Riedel reports today that DreamWorks’s fart-filled Broadway show Shrek: The Musical has lost more than $1 million since Labor Day. For any other musical, this would mean curtains before Christmas, but because Jeffrey Katzenberg is so personally invested in Shrek — which was once meant to challenge Disney’s Broadway hegemony — shuttering it after only a year would mean swallowing his ego and admitting defeat. So, says Riedel, Katzenberg may keep it open, writing off the show’s losses as promotion for Shrek movies and merchandise, even though other musicals are waiting for open Broadway theaters. Since those other shows include Green Day’s American Idiot musical, though, we’d just like to point out that closing Shrek would make Katzenberg a total coward.