Continuity mistake: When Carlotta brings the plates for the meal they all have a dome cover with a top handle, but when Sebastian runs across the table those handles have changed. (00:54:50)
Continuity mistake: When Wallace races to get crackers, check the packet's logo. When the camera angle changes it's different. (00:08:57)
Continuity mistake: The snowman hits his nose with a hammer, completely bending it in half. In the next shot it is suddenly magically straight again.
Continuity mistake: When Charlie and Itchy are escaping from the pound they are trying to dig under the fence. Someone is shooting at them and blows a huge hole in the fence. When the camera cuts to another shot of them going under the fence, the hole is now gone.
Continuity mistake: Tanya O'Tabby's dress sleeves come and go when she's speaking to Sam Spayed (Garfield) for the last time. (00:25:00)