Continuity mistake: Before Elmer runs off to fetch his gun, you can see there is a carrot near his feet on the ground. But when he returns, the carrot has gone.
Continuity mistake: When Elmer has finished making the robot, you can see there is nothing by the slot in which Elmer feeds pictures. But when the robot goes to the donkey, a dial appears where it remains for the rest of the short.
Continuity mistake: When the robot tries to punch Bugs, you can see there is nothing behind Bugs, but in the next shot a fence suddenly appears.