Corrected entry: When Gromit is looking at the penguin's plan to steal the diamond, there are some pencils at the corner of the poster near where is says "Museum", but in the next shot, these pencils disappear.
Corrected entry: When the penguin comes to inspect the museum, all he brings is a pad of paper and pencil (we see this as he is walking by the café) but suddenly when Gromit spies on him he has a tape measurer with him. Just because this is a cartoon doesn't mean that the characters can pull things out of nowhere.
Corrected entry: The penguin's eyesight ability keeps changing. At one point, he takes out a book called "Electronics for Dogs", and since he ends up switching the controls that are attached to the trousers onto switched to a remote, it's obvious that he can read the small print in the book. Also, when he comes to inspect the museum, he takes detailed measurements with a tape measurer. But when he stares at Gromit, who is hiding under the box, and Gromit blinks, he walks away without doing anything. And when Gromit is peeking at the penguin from under the covers and sees for the first time with the rubber glove on, the penguin doesn't see him.
Corrected entry: When Gromit looks at the calendar, he has a watch on his right arm. It disappears in later shots.
Corrected entry: When Gromit is on the couch and then stands up you can see a fingerprint on his head.
Corrected entry: When Gromit leaves his house, he brings a comb, a bone, and an alarm clock with him. Yet before he comes back to the house, he is shown with a newspaper, a knife, and coins. None of these items are even included in Gromit's hut. So where did he get these things from?
Corrected entry: During the train scene at the end, the penguin fires three shots at Gromit, and each time it leaves a mark on his helmet. But suddenly there is a shot of Gromit and his helmet only has two marks.
Corrected entry: There is more jam on Gromit's head than there is flung from the jar.
Corrected entry: When the bread pops out of the toaster, the center of the toast is very black. Then when Gromit has it, we see that it is nice and brown, even though we should have been able to see the black parts.
Corrected entry: During the train scene, Gromit is dangling from a lamp on the ceiling. Then Feathers McGraw shoots the lamp, Gromit falls onto the train, and the lamp is on his head. But as earlier seen, there is a light bulb in the lamp, so shouldn't we have seen and heard breaking glass?
Corrected entry: When the penguin tries to rob the diamond, he uses a mechanical arm from inside Wallace's helmet to grab the diamond. However, the arm is not very precise, and Wallace needs to be exactly over the diamond to get it. When the diamond falls from the mechanical arm, it falls slightly to the right of the arm, but the arm is able to grab it. This is not possible. The penguin did not move Wallace to get it, and even if he had, this would have taken a few seconds, by which time the diamond would have definitely struck the floor.