Continuity: When Conrad first puts the spider lock in his pocket it is put in his left pocket, but when he takes it out, he takes it out of his right pocket.

Continuity: Right after the Cat, Sally, and Conrad crash, Sally's hair bow is half way down her pig tail. In the next shot, it's back on top in a perfect bow.

Continuity: At the end of the movie when the Cat finished cleaning up the mess and was packing Thing 1 and Thing 2, everything looks immaculate except in one scene, in the corner of the living room, there are still purple splashes.

Continuity: In the scene when the Cat is with the kids in his car, right after they show his new steering wheel being a chain linked one, the next shot shows it as a regular steering wheel, and then back to a chain linked one for the rest of the scene.

Continuity: When thing one and thing two come and they start messing everything up, they get the cupcake mix from the previous scene on Sally and Conrad, but in the next shot it's gone.

Continuity: In the scene where the cat's tail accidentally flips Sally onto the couch,we see that the couch is very far away from where the cat is, yet after a 2 to 3 second shot of a CD player coming out of the cat's hat, we see Sally standing behind a chair right in front of the cat, this is impossible as no human can move this fast.

Continuity: During the Cat's fun song, the fish states that 17 of Joan's rules had been broken. However Joan only gave 5 rules, this includes Sally's single rule and "no one sets foot in the living room".

Continuity: When the cat is going into the living room, there are at least 6 pillows on the couch but when he says he's gonna take a look under the hood, all the pillows are gone.

Continuity: When the children hear the bump coming from upstairs, they go to investigate. Spencer Breslin's character says "it sounded like it was coming from the closet". The closet is facing the stairs when they go up them. Later in the film, a shot is shown where you can see the rooms in the whole house together. The closet isn't on this shot, so where has it gone?

Continuity: When the Cat is juggling all the items in the beginning, he has a cake on his hat. After he burps and everything flies up he catches everything but the cake is now gone and never appears again.

Continuity: After the cupcakes explode out of the oven you see the purple goo splash the dog all of its face and left side. However, the next time you see the dog there's hardly any purple goo on him, just a little bit on its face.

Continuity: When Cat fills up the cupcake tray it is very messy with cupcake batter all over the tray but when he closes the tray it is clean and perfect with the batter in each cupcake holder perfectly.

Continuity: The first time Lawrence comes in (as the trio are jumping on the couch), he starts sneezing while standing under the Cat. He's in the middle of the living room and facing the front entry; but in the next shot, he's on the edge of the living room and facing in. He jumps back and forth throughout the scene.

Continuity: After Cat reads the three plans to Conrad and Sally, the "Plans Folder" disappears from Cat's hand after they run away from their hiding spot.

Continuity: In the scene at the birthday party, when the trio is at the window looking inside a shot shows them turning and yelling. It goes to another zoomed out shot, but they turn a second time.

Continuity: When the Cat sees Conrad's mom his hat gets all scrunched up, but in the next shot his hat is straight again.

Continuity: When Konrad, Sally, and the Cat are jumping up and down on the sofa, on the table next to the sofa, the book next to the lamp keeps changing position. It's close to the lamp, then near the lamp, sideways, longways all during the scene.

Continuity: In the scene where the cat is a piñata, the actual piñata has no opening showing the candy. Later when the cat is screaming Conrad sees the piñata with a huge opening on the belly where all the candy are showing.

Continuity: In the scene where they are trying to catch Thing One and Thing Two with the oversized nets, Sally and Conrad get caught in the nets. Thing One and Thing Two then throw the dog out of the window, and it shows us the dog landing outside. When it goes back inside Sally and Conrad no longer have the nets on them.

Factual error: In the scene where the kids are viewing the cupcake baking, there is a sign in the corner reading "laugh". The sign is facing towards the chef, when it should be facing the crowd.