The cats test their formula successfully on Scott. But within minutes, he shows no effects when holding Lou.

When Scotty is kicking the soccer ball, after tryouts, in the back yard, at first his net is square with an ex in the middle of it placed next to a wall. When the shot is panned out, the net is circular with no ex and is in an open part of the yard.

When the cats pull up to the gate of the flocking company in the limo, there are two men standing and talking on the other side. A moment later, when the limo drives through they are nowhere to be seen.

When Brody comes upstairs after missing his son's soccer game, he is wearing a complex face mask, with lots of wires. In silhouette, seen from outside, the visor and wires are missing.

The ninja's goggles disappear and reappear between shots during the fight.

When the dog agents are trying to break into Professor Brody's Lab, the camera shot changes to the dog's point of view. He explains that he doesn't know which wire to cut (as all of his vision is in black and white), but dogs do not see in black and white - their only visual impairment is that they see in the same way as a human with color blindness.

When the dog cuts the hole in the barn floor, technically, when he returns down the hole ("and for God's sake, don't forget to wag those tails") the cut out circle should have fallen back down as there was nothing holding it in place.

When the hole is cut in the floor of the barn to insert the new puppies a large circular saw is used to cut a circular hole. This sort of saw cannot cut this sort of hole.

At 47 minutes Lou the beagle changes from a girl to a boy and back to a girl in three straight scenes.

Lou the beagle is a male dog, and in most scenes a male dog is shown. However, in two belly-scratching scenes a female double is seen.

When Butch is complaining about the mix up with Lou, he says that Lou is so young that he still has his "you know whats", implying that Lou has not yet been neutered. However, the dog playing Lou is clearly neutered.

When the cats drive into the factory you can see the tire marks from previous takes. It is extremely unlikely that such marks would be caused by normal slower moving traffic, especially considering the erratic route.

When Lou says, "Oh. Of course." his mouth doesn't move.

In the alternate ending Mr. Tinkles is seen wearing a prison outfit. When he first arrives at the vet to be neutered he isn't wearing the prison outfit.

When Mrs. Brody was surprised to see Lou and Stealth poop thinking he pooped on the carpet, she said in exclaim "Lou!" but her mouth doesn't move.

In the beginning of the film when the Brodys pull up to their house, the jogger running by says hello to them, but her lips don't move, nor does she face the family's car or general direction.

On the pier when the phone is ringing you can see a man leaning in from the left side of the screen.

Human driver can be seen from distant shots while driving on the factory grounds.

In a top-down shot where Lou jumps after the soccer ball in Professor Brody's lab, the cameraman's partial hand, blue jeans and black leather Chelsea boots can be seen on the far right of the screen.

When the map shows where Buddy is retired the crosshairs pinpoint the location of Boca Raton, Florida in the northeast region of Palm Beach county. Boca Raton is located in the southeast region of Palm Beach county.

Male calico cats are rare or non-existent enough to make the term "male calico" an oxymoron. The male cat named Calico (voiced of Jon Lovitz) is a tabby, not a calico.

The cat referred to as Russian Blue is not a Russian Blue at all. Russian Blues have green eyes and this one had copper eyes, possibly making it a Chartreux.

Mrs Brody refers to the Russian cat as a male when introducing it to Lou, then switches to female.