(at around 1h 23 mins) Kale carefully removes the duct tape that is wrapped around his face. But he just pulls off the rest of it with ease when in reality it would have been tightly stuck to his hair.
The first time that Ashley goes into Kale's room when Kale and Ronald are trying to clean it up, Kale puts a shirt on top of the tower of Twinkie, but in the next two scenes the Twinkie tower is uncovered then covered again.
When Kale breaks into Mr. Turner's house with the garden shears, he cleanly knocks out the full pane of glass. But, when Officer Gutierrez responds to the call, he sees large shards of glass still in the window pane of Mr. Turner's house
When Kale first falls through the boards and into the pit under Mr. Turner's house, the water is very dirty and murky. Shortly after, when Mr. Turner falls into the pit himself, the water in the pit is very clear and clean.
When Kale and Ashley are watching Turner together for the first time, they are talking about what they see in his garage. When Ashley notices the ball, the door is only starting to close, however in the previous take it was almost closed.
Kale's tracking device already started beeping when Kale goes to Turner's house in an attempt to save Ronnie, but everything is silent when Kale is waiting outside of Turner's door with a baseball bat.
When Ronnie breaks into Mr. Turner's car, he uses a paint scraper to prise open the window trim and piece of wire to pop the lock. When he exits the car, the paint scraper has disappeared, but the wire is still in place.
You can only see the top 2 inches of it sticking out of his pants but Kale's underwear keeps changing back and forth between white boxer-briefs and plaid boxers. These scenes were probably shot or re-shot on different days and nobody thought to keep the same underwear that's sticking out of Kale's pants the same.
Kale sees Mr. Turner's reflection on the Apple Cinema display in his room. Apple LCD displays have a non-glare finish so a reflection would not have appeared. The display didn't appear to have a reflective surface in earlier shots.
When Robert got into Ashley's car and locked the doors via the
key less transmitter so that she couldn't get out, after talking to her, he exited the vehicle without unlocking the door. The alarm wouldn't have sounded because he had started the car but he still should have had to unlock it before getting out first.
When Ronnie pops the lock on the suspicious neighbor's car, it does not re-lock. All late model Lexus vehicles automatically and instantly re-lock upon popping the lock. Further, the alarm would go off.
Kale takes apart a "portable home video security system". It would appear that he's removing the 2.4GHZ transmitter and then wiring it MacGyver-style with a 9V battery to his camcorder so as to wirelessly transmit video from that device. Instead he wires the infrared camera and lens to his camcorder, and then magically transmits to his TV.
When iPods are disconnected from audio accessories (docks, earphones, etc.), they stop playback and pause. But when Ashley pulls out Kale's iPod from the dock, he puts it back in and the music continues playback, without him unpausing it.
(at around 14 mins) When the house arrest lady is explaining the ankle bracelet to him she says "they will know where you are 25/7." However, this could have been said by the character to emphasize that Kale's movements are always being watched.
When Kale is walking around his yard marking the area that he can stay in, he makes a square. However if he is only allowed to be within a 100 foot radius of the ankle monitor, the area would be a circle.
At the end, when Kale looks into the air shaft with a light bulb, the ray of light used in a movie is actually flashlight. It shows spots of light, instead of a real light bulb, which would have lit up the entire room.
When Kale's Xbox Live account gets closed, he tries to log back in and gets a "ACCESS DENIED" message. But if his account was closed, he should've gotten a log in error message, saying that his username or password was incorrect.
When Kale and his dad are in the accident in the beginning of the film, their overturned SUV is hit by a second vehicle. In the wide shot of Kale exiting the SUV, you can see through a hole in the floor that the gas tank, spare tire, and other essential components of the truck are not there. They had been removed (presumably for safety and weight reduction) before the accident.
When Kale's Xbox Live account gets closed, he tries to log back in and gets a "SERVICE ERROR" message. But if his account was closed, he should've gotten a log in error message, saying that his username or password was incorrect.
The goof items below may give away important plot points.
When the cop draws his weapon before he gets killed you see him pull it out of a military style "full flap" holster which completely covers the pistol. Civilian Police would never use a holster that restricts access to their firearm.
In the scene where Kale and Ashley are in his room and Ashley tries to dial the phone for the police but the connection is dead, the power goes out. Kale and Ashley then hop out of his window, onto a garage/shed roof, and into Ashley's pool in order to go out of the 100 foot perimeter and for the police arrival. However, as soon as the power went out in Kale's room, the police should have already been notified due to the ankle receiver plugged into the wall downstairs. In a previous scene, an officer said, "don't try to unplug it or the police will come in 25 seconds."