Factual errors: When Rocky is battling Fester in the master bedroom, his reflection is seen in a mirror. The mirror is hanging on a wall facing the door, away from him, and should not have caught his image.
Factual errors: When Snyder is escaping in his helicopter, Sam Douglas fires nine shots at him from a six-cylinder revolver.
Continuity: When the kids use the plunger on Hammer's face, Hammer's hair is pulled over his face. In the next shot, his hair is back in a ponytail.
Audio/visual unsynchronized: When Snyder whistles for his henchman to stop attacking the kids at the grandpa's house his fingers are two inches away from lips when the whistle is dubbed
Plot holes: Lester, Marcus, and Hammer wake up in their van while Rocky, Colt, Tum Tum and Emily ride by yelling. Hammer says, "Dude! There they go!" however, he hadn't seen the kids yet. How did he know they were the right kids?
Errors made by characters (possibly deliberate errors by the filmmakers): When Colt is in his dad's study and his mom is talking to him while putting on her earrings, when she leaves, you can see her earring fall off.
Continuity: In the scene when Emily gets her bike stolen. One shot show the brakes on the handle bars and the next shot the brakes are missing.
Factual errors: The kids use a tin can telephone throughout the movie, but both ends are mounted on lamp stands with the cable being loose. Tin can telephones only work if the cable is taut. Otherwise, the vibrations wouldn't reach the other side.
Continuity: When Tumtum is playing Super Mario Bros. 3, we see the screen four times. Every time we see the screen, he is at a radically-different point in the game.
Continuity: During Snyder and Grandpa's fight, Grandpa knocks Snyder's sword out of his hands. In the overhead camera shots that follow, the sword is still there on the mats, but in the "from the side" camera angles that follow, the sword is gone.
Audio/visual unsynchronized: Snyder's helicopter doesn't make any noise until it appears on screen. Helicopters are extremely noisy vehicles, and it should have been making noise, even out of the angle of view.
Continuity: Brown tells Fester that the Douglas' address is 623, but when you see the kids running out the house the number in front says 580.
Colt was originally named Pony.
The video game the boys play in their room is Super Mario Bros. 3 for the 8-Bit Nintendo NES System. Similarly, the box for this system appears in the boys' closet later in the film.
Hammer wears a Metallica shirt and puts up stickers of the different Metallica albums in the phone booth.