When the angry neighbor appears at Elmer Fudd's door for the first time the door hinges are located on the left of the door frame. Earlier on Elmer Fudd enters the same door but the hinges were on the right side of the door frame.
There was no keyhole on the bathroom door when Bugs first enters. It appears when Elmer wants to look through it.
When Bugs Bunny kicks the shotgun away with his feet the gun appears to magically pass thru the legs of the outdoor table.