Continuity mistake: When Turbo is about to go down the curb after nearly getting killed by the lawn mower, you see him lined with the 2, he's on the left side of the 3.
Continuity mistake: The protagonist at the beginning of the movie sunbathes topless.The camera is positioned where the kid is spying her, and in that wide shot she is placing the garment she removed close to her lower half of the body. When he waves his hand casting a shadow over her eyes, the bikini top is in the corner of the towel next to her head. (00:01:20)
Other mistake: Throughout the film, you can frequently see many people's faces blurred, phone numbers blurred, store-fronts blurred, etc. This is because the production could not afford the rights to show these people, places and things, and simply blurred them out.
Continuity mistake: After stabbing the bad guy at the beginning, Callahan for some reason pulls back and somehow dives past a door managing to drag in a grown woman who was all crouched down by the entrance. Wonky physics of it aside, the bad guy shoot at him, but shoots just a hole in the door frame. The hole appears to be CGI, and in fact when Callahan shoots back from the bedroom, the hole is gone. (00:01:35)
Factual error: There is a shot in the movie showing the outside front view of the Apple Head Office building. At the bottom of the screen it states the year (1981 or 1982). As the year is posted on the screen, a Chevy Cavalier drives into the shot in the foreground parking lot of the property. The Cavalier's style/shape and front headlights reflect that of a 1992-1994 model car - not a car from 1981 or 1982. (01:04:20)
Continuity mistake: When the movie starts and Linda takes a glass of water to her lips, the hand with which she holds the glass swaps between shots.
Continuity mistake: The protagonist is told about the budget cuts that will lead to the library shutting down. During the scene, the strap of his hat keeps going back and forth in front / behind his ear. (00:02:05)
Continuity mistake: In the scene at the beginning where Simon Yam is telling Karen Mok that the case she is working on is closed, as he holds her shoulder to turn her towards the door in one shot, and her hair is completely at her back behind her shoulders, but as he turns her around and the shot changes, her hair on the left side is seen over her shoulder in front.
Continuity mistake: As El Camaleon pulls the Cuba Gooding Jr. face off, there's an unshaven neck with a tattoo visible under it. After the cut, Lady Gaga's face (also presumably unshaven admittedly, but not visibly so) comes to light under a mask of visibly lighter skin tone. (00:45:05)
Plot hole: When the robot pilots first connect after the first attack, Red tells the story of his battle. They don't seem to even notice the dozen or so civilian bodies they have to actually physically step over - and the bodies are just lying there along the sidewalk & parking lot; no signs of any monster attack, so how did they die?
Continuity mistake: Our group of jewelry thieves are on their way to "Zugarramurdi" in a stolen taxicab. The "green soldier" Antonio began to wash the color from his face. Nevertheless you can see, depending on the camera angle, that the green color is sometimes seen on his nasal bone and sometimes not. (00:20:55 - 00:21:30)
Continuity mistake: When Keisha shows the father the painting she made, the father places it on the table over the color palette. Then after Keisha screams in the father's face, the magazine is gone. He sprays her with breath spray and replaces the painting over the color palette. (01:07:00)
Factual error: The movie takes place in Carolina Beach, N.C. (east coast), and yet a number of times the protagonist, and others, sit on the beach and watch the sun setting over the ocean.
Character mistake: Spanish headlines are seen. Some of the a's have the wrong accent on them ("å" instead of "á"). (00:45:25)
Revealing mistake: When Brooke arrives at the camp to drop off Steph and Chrissy, Chrissy leans out of the car and vomits, but you can see that she's not really vomiting, and is using her hand to cover up the special effects tube.
Factual error: Near the end, Zoe and Trey battle to the death, Zoe armed with a tomahawk and a knife, Trey armed with a Husqvarna chainsaw. During the battle, Zoe manages to amputate Trey's right hand, with which he was gripping the chainsaw's safety release and trigger (as his left hand gripped the support handle). Bellowing in pain, Trey continues swinging the chainsaw by its support handle with his left hand. Lo and behold, the chainsaw is somehow, miraculously, still revving in-and-out, which is only possible if the safety release is continuously depressed with the palm of the right hand as the fingers rhythmically flex to squeeze the trigger. Of course, with all major tendons in the wrist severed, an amputated hand cannot grip or flex or squeeze anything.
Continuity mistake: Notice how Julie pumps her shotgun twice within a few seconds in the lab without once firing.
Audio problem: When the Police play "Roxanne" for Hilly, the actors are just lip-syncing to the studio version; though his laugh has been edited out, the atonal piano chord at the beginning of the song, a now-famous gaffe from when Sting accidentally sat on a keyboard during recording, still remains.
Continuity mistake: At the beginning of the film you can hear a kettle whistling. But when Alvin removes a teapot (not a kettle) from the heat the whistling stops, but when he puts in back on the heat about 5 seconds later there is no whistle. Alvin doesn't remove a whistle cap or turn off the heat. (00:02:30)
Continuity mistake: When the two criminals seen at the beginning kill the drug dealer, he is initially still sporting his sunglasses, rolled at the back of his neck. When they drive away, the shades somehow ended up in a totally different spot around his midsection. (00:03:55)