Continuity mistake: When the McCallister family arrive at the Florida flight and give in their boarding passes, Sondra standing in front of the gap between the man and lady taking the tickets, and then leaving. In the next shot she is standing in the same place again and leaving a second time. (00:12:55)
Revealing mistake: In the scene when the bandits are in the uncle's house at the bottom of the stairs, the tool chest falls down. When it hits the door and they slide back if you look closely you can see that they are on rollerblades.
Other mistake: When Marv ends up stepping on some green gunk that Kevin set as a trap in the basement, he eventually slips and then slides into a shelf of paint. However, Marv actually started sliding after he fell to the ground. It's almost as though he was being pulled forward. How could he have slid?
Revealing mistake: When Kevin arrives at the airport in New York (filmed at Chicago O'Hare) and goes up to the agent to ask her what city is outside the window, one of the destinations on the board at the gate is New York - LaGuardia...giving away that the scene was not shot at a NYC area airport.Steven Campbell
Continuity mistake: When Harry and Marv catch Kevin for the first time, coming out of the hotel, they walk away and are standing at the traffic lights. The camera angle is Kevin looking up at Harry and is from below Harry's elbow but Kevin's height makes this impossible seeing as he is up to Harry's shoulder.
Visible crew/equipment: As Tim Curry exits the lift to secretly search Kevin's room, at the bottom right hand corner a shadow that looks like a hand appears on the wall to the left of the lift, inconsistent with the movements of him exiting the lift. You have to be quick, as it appears on widescreen as the shot moves away from the lift doors.
Other mistake: In the scene where Kevin is being chased through the Plaza lobby, the large brass/marble table, usually in the center of the room, has been moved to one side to allow the characters to freely run through the area. The table has been purposely moved as it is right next to the concierge desk which would pose an inconvenience to any guests and so, therefore, is not a natural occurrence. After all three fall over, it is evident that a large space has been cleared, as it allows for Cedric to be dragged away as well.
Continuity mistake: Kevin is being served ice cream in his hotel room. A wide shot of the bed shows the food around it and the waiter scooping ice cream into a bowl. Look at the tall pink rose at the end of the bed, which towers out of its vase. In a couple of shots later, the rose suddenly becomes barely higher than the vase itself. (00:33:30)
Continuity mistake: When Marv has just climbed out of the basement through a hole in the floor, we see him dangling facing forwards, but the shot of his legs below gives the impression he's facing sideways. He has no time to switch positions between both shots.
Continuity mistake: When the McCallisters are at the police station, the cop puts downs the phone and tells them there is "No sign of him." Behind them, the coffee pot is half full and a lady in a multi-coloured top talks with another cop. In the next shot of the McCallisters, the coffee pot is almost empty, a coffee tin with a red lid appears (that was taken away in an earlier shot) and a completely different lady talks to the cop behind them.
Continuity mistake: Take a look at the position of the penknife when Kevin is paying for the toys and chatting to Mr Duncan. In one shot it's in line with the camera, on its front. The next shot (10 seconds later) the penknife is on its side and lined up with the book. Mr Duncan did not touch them in this time.
Revealing mistake: In the scene at the end when Marv and Harry are talking to Kevin on the roof, if you watch it when Kevin throws the brick down at them, the one brick hits Marv. They cut film somehow so you wouldn't notice easily, but when it hits Marv you can see the corner buckle in, as it's a sponge made to look like a brick.