When Wile E. Coyote first takes the pressure cooker top to install over Bugs' hole, there are five screw holes showing around the perimeter. However, from then on, only four screws are ever screwed in - first, when Coyote screws it in, he screws two pairs in, then he unscrews two pairs, then Bugs screws in two pairs. Finally, when Bugs clubs Coyote from underneath, popping the cooker off, it shows only four screws.
When installing the pressure cooker top over Bugs' hole, Wile E. Coyote turns the wings of the screws, but they don't move - until after he lets go of them, then they sink down to their final position.
When Bugs presses his plunger down to detonate his decoy coyote, the wires from the plunger move as if something solid were being sent through them. In actuality, the electric pulse sent by the plunger would not make the wires move at all.
When Wile E. Coyote romances the time bomb decoy that Bugs Bunny sent for him, the decoy's cigarette repeatedly turns green and white.