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.
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.
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: 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.
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.
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)
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)
Factual error: Kate flies American Airlines to Scranton, but that airline did not serve Scranton in 1990. Also, a DC-10 is too big to be serviced at Scranton.
Suggested correction: Air Force One, which is quite a bit larger than a DC-10, has landed at Scranton in the past (https://wnep.com/2013/08/22/air-force-one-lands-in-scranton/). Just because DC-10s don't generally land there doesn't mean they can't.
They are much more likely to make an exception for Air Force One than the are for a single family unless it was for something wrong with the flight or an emergency on the flight, not for a connecting flight to Chicago or a chance at a connecting flight.
The idea is that DC-10s can land there for whatever reason.
Kate landed at Dallas first, then flew to Scranton. This is revealed in Kate's rant at the ticket agent.
Air Force One would park at GA parking, not at the terminal. The DC-10 that lands would have very likely parked at a gate for only 737s and smaller.
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.
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 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.
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: 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.
Factual error: When Kevin's mom stays behind at the Paris Airport to wait for a flight home, she is shown in a gate area in front of a huge picture window. Outside can be seen an aircraft, a 727 in Eastern Airlines livery, in what is actually Chicago's O'Hare Airport. Eastern never flew to Paris and the aircraft would not have the range for such a flight. Also, you can see a sign that lists Terminal E and F, which are at ORD. They do not have these at Paris ORY.
Continuity mistake: In the scene where Kevin goes flying into his treehouse and breaks out the wood, the amount of wood missing changes from one scene to the next.
