Continuity mistake: As Buddy walks out into the street at the start of the movie when the cat is playing dead, you can see several parked cars on the street behind him. When the van backs up to 'catnap' buddy, there are no parked cars. Then as the van drives off again, there is a different bunch of parked cars in the street. (00:03:54)
Deliberate mistake: When the Russian cat sets the bomb on the big metal door, it is set for one minute. Yet this one minute seems to take three minutes to count down. I know it would be boring if it really was one minute, but why didn't they just make it so the cat set it to three minutes? (00:45:00 - 00:50:00)
Continuity mistake: When the video of Mr. Tinkles threatening to 'put the Brody family to sleep' is seen in the background at HQ, it is noticeably different to when the dogs saw it first time. This is easier to verify when Mr. Tinkles says, 'they will be put to sleep.'
Factual error: When the Russian Blue is in Luke's house, there is a shot where Butch is tangled up in the telephone wire but it should actually be mirrored since it was the reflection in the cat's eyes.
Continuity mistake: When Lou walks knocks the door into the burning room where the kid and his parents are, you can see that Lou has a circled chain. However, in the next few shots it appears as a bone shaped chain and then it changes back to the circled chain. (01:14:40)
Continuity mistake: When Buddy the Bloodhound is chasing the ginger cat through the womens' house at the beginning, you see a shot of the cat from Buddy's point of view which shows the cat sitting down. Yet in the next shot that zooms in on the cat, it is standing up. (00:03:10)
Continuity mistake: In the scene in the flocking factory when Jeff Goldblum's character is being confronted by the cat leader (Mr. Tinkles) another cat (Calico) is on Goldblum's shoulder. When the shot changes to an angle behind Goldblum, Calico disappears only to immediately reappear when the shot changes back to the angle facing Goldblum.