Other mistake: In the intro to the Pastoral Symphony, the narrator identifies the deity who cloaks the world with Night to be Morpheus, who is the Greek god of sleep and dreams. However, the character in the animation is fairly obviously female, with long hair, eye shadow, and lipstick. My theory is that the character was intended by the art team to be Nyx, the Greek goddess of Night. Night would be a more likely candidate to be making it nighttime across the world, while Morpheus would be more likely to put people to sleep or send them dreams.
Continuity mistake: When Porky parks his car after the security guard spots him wearing an Oliver Hardy disguise, he jumps out of the car and the door is shut. When Porky sees the security guard after being thrown out of the shooting of the ballet film, he runs back to his car and the door is now open.
Continuity mistake: When Elmer places the carrot by Bugs' home, the rabbit tracks around the hole keep disappearing and re-appearing between shots.
Continuity mistake: When Elmer is reading his book at the beginning of the cartoon, you can see it reads "How to Photograph Wild Life" on the spine, but when we see Elmer in the next shot, the words have gone.
Continuity mistake: After Mickey hides Pluto in his suitcase in Burbank, Mickey picks up his cane and runs to the train, then when Mickey actually jumps onto the train caboose he's only carrying his suitcase, he does not have his cane, nor does he have Pluto's suitcase (which had been filled with bones) with him. The cane reappears on the train later, and at the end Pluto's suitcase mysteriously reappears when Pete throws it at the duo in Pomona.
Continuity mistake: After the mouse is revived by water from Jasper, he goes up to the cat and you can see that the mouse's left hand is under Jasper's mouth, but in the next shot his hand is now near the whisker area.
Continuity mistake: When Papa Bear is drinking from the hot water tap after eating the hot porridge, the tap handle changes position between shots.