Continuity mistake: When Gordon and Benny are in Stephanie's apartment with James, you can see the clock behind Benny, but a few of shots later the time has changed to being earlier.
Continuity mistake: In the pet shop, Gordon gets all wrapped up with plastic wrap. Just a few short scenes later it's gone. There's no way he could have gotten himself out of it in that amount of time. Also, the "plastic" fishbowl shatters - plastic fishbowls like that are not that rigid and would not break like that. Add to that the "piranha" tank is obviously a bubble line at the back of the tank - you can see the bubbles come up when they reach the fishnet in.
Continuity mistake: During the end of the movie, spot is in the park again, and when he looks at the bad guys, he has a collar on and then when he looks back, it is off. This happens for a minute or two.
Continuity mistake: Towards the end, the mail truck has a reflector hanging outward on the driver side. Later scenes, it's back in place.
Continuity mistake: When the boy gets a call from his mom, she is far away from the truck. When it spits mud up, she is right next to it.
Continuity mistake: When Gino and Arliss are given the contract to kill Agent 11, note the distinctive pattern on the shirt Arliss is wearing - particularly the collars, which keeps changing even within the same scenes. Though the actor's wardrobe consisted of black shirts of the same style, their patterns varied. For example, during the scene at the pet store there are at least three different patterns seen on his shirt. The same thing happens again later with a different shirt Arliss is wearing, after the scenes of Gino and Arliss at the dog training facility.
Continuity mistake: When Gordon tastes the bran cereal with soy milk and prunes, the cereal box is on the table beside the soy and regular milk containers, but when he's gagging by the sink the cereal box has vanished in the shot facing James, and then it reappears. Things on the table change position as well, such as the soy milk turning itself around.
Continuity mistake: When Gordon fixes himself the bowl of bran cereal with soy milk and prunes, he places the orange cap back on the soy milk, but when he tries to eat the cereal and spits it out, the soy milk cap is gone (the gallon of regular milk has a pink cap behind the capless soy milk). Then it's back on the bottle, before it's off and back on again.
Continuity mistake: Tyson, the dog on the chain, escapes and snaps the chain right in the center. When he reaches the tree, the remains of the chain are gone.
Continuity mistake: In the opening sequence, the driver's door on the mail truck is wide open. When the protagonist arrives at his destination a moment later, the door is closed.
Continuity mistake: In the first scene the little boys mom is covered in mud then it switches to Gordon then it goes to her again and she is hardly covered in mud.
Continuity mistake: When Benny takes the Polaroid photo of Gordon, James, and Spot, their positions differ in the resulting photograph.
Continuity mistake: When Stephanie steps into the petting zoo trailer her right sleeve is rip-free, but in the next shot as she walks in and takes a seat on the bale of hay, suddenly there are 2-3 large holes in her right sleeve.
Continuity mistake: When Gordon goes looking for James, who ran off to find Spot, there's a sticker on the wall behind Gordon in the closeup which vanishes in the following shots, but reappears when they're in the mail truck together.
Continuity mistake: While Gino and Arliss are at the restaurant stressing about finding the dog, Gino tells Arliss that he hates Tommy because he has no respect, and when the cell phone rings two cans of dog food suddenly appear on the table in the next shot.
Continuity mistake: When Spot witnesses the purse snatching he's suddenly wearing a collar, which promptly vanishes again.
Continuity mistake: When Agent Sharp switches the ID tags on the animal crates, the ID tag on Agent 11's bars changes position between shots.