Revealing mistake: When Harry tells Marv to go back while they are climbing across the rope, in the shot facing them front-on, you can see Kevin in the background about to cut the rope. If you look closely this is not Kevin, it is his stand-in.
Continuity mistake: When Marley comes into the drug store to see Kevin, the wrapping paper is leaning on the shelves, but in the next shot the wrapping paper is gone.
Continuity mistake: When Kevin puts the spider on Marv's nose you can see a box of junk is almost halfway off the steps of the attic but in the next shot at the start of the film the box is no longer halfway off the steps.
Continuity mistake: When Kevin is washing dishes, there's Bubbles on his hands, but in the next shot there's no bubbles on his hands.
Continuity mistake: Harry and Marv both get hit with the paint containers on the stairs. Look at the front doorway when Marv gets hit. The cord (from the hot implement attached on the doorknob) is in an 'S' shape and lots of micro machines litter the doorway. Harry then gets hit. When he gets up to go up the stairs after Kevin, the cord has moved and the micro machines are well clear of the doorway.
Continuity mistake: When the 2 burglars are breaking into the McAllister home, the tall burglar gets hit square in the face by an iron...he has iron marks on his forehead and cheeks but not his nose...how could the iron not hit his nose?
Other mistake: When Gus Polinski talks about his music, he mispronounces "Daj mi buzi" (Die-Me-Boo-Gee) as "Domavougi." "Daj mi buzi" is Polish for "Give Me a Kiss."
Suggested correction: I think this is meant to be a "deliberate mistake ", which didn't show up as an option to suggest making the change elsewhere (under "edit"). It appears to be part of the comedy - he should know how to pronounce it. Another opinion would be helpful.
Continuity mistake: When Frank squishes Fuller with the chair, we see Frank walk off. However about 5 seconds later we see Frank's wife rescue Fuller, and Frank walks off again. (00:09:35)
Suggested correction: Not a mistake. Frank never walks off the first time.
Perhaps the wrong phrase was used. He actually moves away from the front part of the seat to the left and out of shot of the camera. When the shot is shown of Frank's wife rescuing fuller, Frank repeats his actions of walking away from the front part of the seat and moving to his left. There is no reasonable reason he would move back in front of the chair for the purpose of repeating this action. Especially since his wife is trying to rescue Fuller and would not permit Frank to return to his original position. So the mistake is valid, just an error in wording.
Continuity mistake: In the supermarket when Kevin puts the groceries on the conveyor belt, he sets the tissue paper standing up. The next shot of Kevin shows the tissue on its side and farther back, the next shot it's back to its original position.
Continuity mistake: Right before Kevin destroys the shelves after climbing up to reach the metal box, the box with Buzz's life savings (on top of the shelves in his room) moves between the overhead and ground shots.
Continuity mistake: Kevin's hands change during the micro-machines sequence. He is sitting at the top of the steps, and puts his right hand down. In the next closer shot, both hands are in a different position.
Continuity mistake: After Kevin's whole family comes home, he walks straight to the window to look out. If he had done that, he would be looking out of the side of the house, but he is obviously looking out the front of the house to straight across the street.
Continuity mistake: When the delivery guy stands outside the door and Kevin plays the movie, in the shot from Kevin you see the red curtains are more wide open and you see the silhouette from the delivery guy. In the shot from the delivery guy the red curtains are suddenly more closed and his silhouette couldn't be showing through.
Revealing mistake: Towards the end when Harry walks up the frozen stairs, you can see it switches to a stuntman when he slips and lands on his back. (01:17:55)
Continuity mistake: When Kevin puts the groceries on the belt, there's 2 packs of toilet paper. One in the front and one in the back behind the orange juice. When she scans the orange juice, the other pack of toilet paper isn't there.
Revealing mistake: When old man Marley hits Harry and Marv with the shovel at the end, you can see it's actually a stunt man doing the hitting motions.
Continuity mistake: Buzz comes down the stairs 3 seconds before Kevin, but manages to eat Kevin's entire cheese pizza in the next shot before Kevin could enter the kitchen. (00:08:04 - 00:09:20)
Continuity mistake: When Kevin climbs on the shelves in his brother's bedroom you can see the spider switch to left and right.
