Continuity: 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.

Continuity: It is clear throughout the movie that the dog that plays the character "Lou" changes from a male to a female. You can tell in different scenes when Lou is standing up, it's a male dog, and when Lou is laying on his back, belly facing up, it is a female dog.