Continuity mistake: When Marv comes to the back door while Kevin is washing dishes, Kevin turns on the Johnny & Snakes movie. Then he goes to get the pot and puts the pot by the back door. The whole time he has his sleeves rolled up, but when he opens a drawer to get firecrackers, his sleeves are rolled down. In the very next shot they're rolled up again. The shot changes too quickly for him to roll them back up.
Continuity mistake: In the scene where Kevin is hanging up ornaments on the Christmas tree and he sees Harry peeping through the window by the reflection of the ornament, the reflection is not entirely accurate. It shows Kevin facing the camera with both the tree and window behind him. The reflection should have shown Kevin with just the window behind him and slightly to his right, based on his original position.
Continuity mistake: When Kevin is searching in Buzz' chest, some objects appear or change place after he throws the Playboy magazine away. (00:21:45)
Continuity mistake: When Kevin says, "I made my family disappear" and runs around the house, he runs to the foyer and spins in a circle. The window near the stairs is dark meaning it's dark outside. He run upstairs and the window in Kevin's parent's room is also dark. The lights are on too. He then goes to Buzz's room and the kitchen and it's light outside. No lights are on.
Visible crew/equipment: When Kevin first realises he's home alone and goes into Buzz's room, there is the leg of a crew member to the bottom right of the picture (wearing jeans). (00:19:20)
Suggested correction: Not visible at all.
Continuity mistake: Right after Marv loses his shoes on the tar covered stairs he goes back outside to go in the window. When he's running in the snow you can see that he is wearing little pink booties so his feet don't get cold. When he is getting into the police car at the end, you see a short shot of his feet when he's almost in and you can clearly see he has black boots back on.
Revealing mistake: When Kevin screams from putting on aftershave, the shot cuts to the spider running behind the toilet. You can see white tiny pellets being thrown at the spider from behind. This must have been to make sure it kept moving during the shot.
Revealing mistake: When Marv is about to hit Harry, who has the spider on his stomach, you can tell that, for two shots, it's a fake spider. The real spider is brown. In the shots where Marv is standing about to hit it, the spider is black and motionless. (01:26:00)
Continuity mistake: The plane for Paris leaves in the morning - around 10 am. Shortly after take-off (it is still morning in Chicago) it is dark outside the windows. Even though the flight path from Chicago to Paris goes a bit north, it would not get dark that fast.
Continuity mistake: When Kevin plays the video when the guy comes to deliver the pizza, the guy on the video says "Hey. I'm gonna give you to the count of ten." When Kevin first saw the movie, the word "Hey" was never spoken. The line immediately before "I'm gonna give you to the count of ten" was "I'll tell you what I'm gonna give you, Snakes".
Other mistake: When Harry and Marv are making their way across the rope to the tree-house, you can see them dangling in a long shot. It has to be stuntmen because, despite the 12 inch height difference between the characters, they seem to be the same size while hanging there.
Other mistake: Toward the end of the film, there is a scene where Macaulay Culkin rides a rig on a rope from his house to the treehouse. Joe Pesci and Daniel Stern try to follow, but Culkin cuts the rope with a hedge cutter. Problem is: The rope is slack when Mac cuts it. With the weight of two grown men, it would have been stressed like a guitar string.
Audio problem: When Kevin is going through Buzz's private things he finds a picture of his girlfriend. Sickened by her appearance, he smashes the picture. But the smashing sound starts before he hits it. (00:22:05)
Revealing mistake: When Kevin lands in the treehouse, he's at the back with his feet through the wall. Given where the rope is tied to the tree, he would have hit into the tree or the door frame of the treehouse, not at the back wall.
Continuity mistake: The Murphy's basement is shown to be dripping water from when Marv flooded the kitchen earlier but when the crooks are hit by the old man at the end of the film, the floor is dry even though the faucets are still running.
Continuity mistake: As Marv loses his last sock on the tarred stairs, his heel does not make contact with the tar. Later, when he picks up the crowbar to walk out, his whole foot is now covered in tar.
Continuity mistake: The amount of tar on Marv's feet changes from all over the bottom and sides, to just the bottom to almost none. Even though he walked through the snow, the tar would not just wash off.
Revealing mistake: When Harry tells Marv that he's sick of him leaving the water running in the house that they robbed, you can see Harry supposedly shift his van into drive. However, Harry does not even move the gear selector from park to drive.
Visible crew/equipment: When the pizza guy arrives at the start, as he gets out of his car a stage light is reflected in the paintwork. This cannot be the street light as that is a more yellow and dull reflection, further along the car. (00:06:50)
Revealing mistake: Kevin goes food shopping, He gets milk and detergent, obviously heavy items. Afterwards we see him walking home and the bags he is carrying break open. He is carrying them like they are light as a feather. Even when the milk falls, you can tell it's an empty bottle.
