Continuity mistake: While dusting off the stage podium, Dewey sees some men walk by leaving a trail of dirty footprints on the stage. He gripes at them and bends down and begins whipping at one of the foot prints. As he does, another guy goes guy wheeling something along that leaves a dirty trail of wheel prints as well as his own footprints between the two lines. This new set is beside the other set of footprints Dewey is already cleaning. It then cuts to an overhead view, and suddenly the first set of footprints vanishes, and Dewey is suddenly in the same position, but cleaning a footprint in the second trail.
Picture added by Quantom X