When Pinocchio is surrounded by sea horses, Jiminy Cricket rides up to him on another sea horse. After it neighs, Jiminy Cricket says, "Steady there, Nelly!" in a regular voice, suddenly his speaking voice switches back to the processing that created under-the-water sound that was used previously.
If you look very closely to the scene where Lampwick looks at his refection at the billiard's mirror when his transformation has begun. You will notice that Lampwick's refection has gray hair while the Lampwick outside the mirror has black hair.
When Jiminy cozies up to sleep on the end of a fiddle, he kicks his shoes off in front of him. But when he is aroused by the Blue Fairy's arrival and grabs his shoes, they are now some distance away, sitting neatly heel to heel.
As he approaches the entrance to the rough house with Lampwick, Pinocchio takes a bite out of the big pie he's holding in his left hand. A few seconds later, just before he throws it away, the pie appears to be intact.
When Honest John and Gideon are taking Pinocchio to Stromboli, there is an above shot of them walking through the street, around a tree, and to the end of the street. Throughout this entire shot, the upper portion of Pinocchio is not colored in and appears brown, as if he lost his color.
The holes in Honest John's and Gideon's gloves switch between their left and right sides throughout the movie. In one of these scenes, however, the hole is not in a pinky - it is in the left-hand thumb instead. In another shot, the fur color of John's pinky finger under the missing glove material is white instead of matching the color of his fur.
The 12-ball on the pool table on Pleasure Island is first white with a dark blue stripe in the first and second shots of Lampwick. The camera then cuts to Pinocchio and back to Lampwick. The 12-ball is now solid dark blue. The 12-ball also keeps moving around on the table randomly without anybody hitting it.
When Jiminy is woken by the clocks and looks at the ones on his right, there is string between the heads of the violin he is sleeping on. When he looks to his left, the string is gone. Then when we see his pupils moving like the clocks' pendulums would, the string is back.
When Jiminy Cricket is flung from the lock hole by a loose spring, he is wearing his coat and hat even though he had taken them off before he went inside to work on it. When he lands they are off again.
Among the balls seen on the pool table are two sky blue ones but in reality there's no sky blue balls in a game of pool. In reality only one shade of blue is used in pool which is either dark blue or royal blue unlike this movie as a pair of dark blue balls are also seen with the sky blue ones.
On some establishing shots of Pleasure Island, the horses on the merry-go-round change color. The color changes are in a pattern suggesting the horses are lighted which is congruent with the rest of the merry-go-round.
After Pinocchio and Jiminy Cricket jump off the cliff and escape back to their town, the boys turned into donkeys remain behind at Pleasure Island. It's unknown what happened to the donkey boys including Lampwick afterwards after Pinocchios escape. Or if they rise up and fight the Coachman villain, Honest John the Fox, Gideon the Cat or escape from the salt mines or Pleasure Island. Also it's unknown where Stromboli is or his reaction to Pinocchio escaping from his cage.
For some reason Pinocchio, Jimimy and Lampwick don't notice the other boys becoming donkeys. Given there were hundreds of boys on the island the trio should have spotted several of the boys becoming donkeys at least. Plus Pinocchio and Lampwick are the last ones standing turning to donkeys especially Lampwick.
The goof items below may give away important plot points.
When Lampwick turns into a donkey, there is one shot where we see the shadows of him and Pinocchio. Lampwick's hat falls off but when the shot zooms out there is no hat on the ground. Also, Lampwick's shoes as well as the rest of his clothes disappear when he kicks the gambling table over.
Pinocchio and Jiminy Cricket escape the coachman and his minions by jumping off a cliff into a body of water. The scene changes and shows the two making it safely to shore, showing they both are capable of swimming. In a later scene, as they are searching for Geppetto, both characters travel underwater for an extended period of time, somehow not exhibiting any side effects (understandable for a magical talking puppet made of pine, but this would have immediately killed Jiminy, a living, breathing insect). However, once Pinocchio rises above the surface, it does not take long for him to drown as he tries to save a semi-conscious Geppetto (who survives, along with Figaro, Cleo and Jiminy).
When Lampwick checks his reflection after discovering he has fur and donkey ears his reflection has gray donkey hair instead of black, especially given his entire reflection has a slightly different tint on the mirror.