Revealing mistake: When Alex says they should go find the penguins, he says "To home" and Marty, Melman, Gloria and Julien place their hands on top of his hand. In the next shot it shows all of them together. But due to the position of Julien and his arm length, it would have been impossible for Julien to have his hand fully placed on Alex's hand. (00:05:05)Casual Person
Revealing mistake: When Scrat removes the giant acorn in Scratlantis the city is immediately flooded. Everyone in the background is blown away by the sudden rush of water. However, both Scrat in the background and Scrat's host (slightly off-camera) in the foreground don't move and don't seem to be affected by extremely strong flow. (01:18:50)
Revealing mistake: When Sparky's tail pops off there is a hole where it popped off. But when the tail goes into the bucket the hole is gone.
Revealing mistake: In the laboratory, when Dex tells the doctor he needs him to analyse what he borrowed from Lady X, it is apparent that when Dex first shows it the doctor, there is nothing in his hand. He just appears to be pretending to hold something. It is not until two shots later, that the object he shows to the doctor is visibly in his hand. (00:37:25)Casual Person
Revealing mistake: During Jack's memories, when he is holding the antlers up to his head, Jack's sister's boot can be seen coming through the fabric of her dress.