Revealing mistake: When Speedy Gonzales is watching Sylvester drink Tabasco sauce from the tank that sends him miles into the horizon, watch Speedy's tail: it disappears before the scene ends.
Revealing mistake: When Bugs is applauding with the audience after Daffy has blown himself up, his tail disappears for a second.
Revealing mistake: After the alley cat has put Fernando in his mouth, Speedy runs back and forth before hitting the cat on his foot. If you watch carefully, you can see nothing hits the cat's foot at all, but he reacts as if in pain.