Audio problem: When Elmer Fudd says "You scoundrel!" to the bear, you can see Elmer's mouth moving after he has finished speaking.
Continuity mistake: Elmer Fudd is wearing his bowler hat when he is making a potion for the bear to drink, but when he takes the potion to the bear, his hat has gone.
Audio problem: When Elmer Fudd is holding down the test tube, he is seen laughing yet no words are coming out.
Continuity mistake: When Elmer Fudd is holding the test tube to drop liquid into the solution, you can see there is nothing on the side of the tube, but in the next shot a measuring system suddenly appears.