Other mistake: The old man that receives Kevin's bag in Florida can be seen walking through the airport when the family runs past him. The man could not have boarded the flight to Miami, as the family ran past him and were the last to board. The man was wearing shorts when he received the bag (but he could have changed on the flight in theory - had he been able to board). An old woman with him was in the same situation. (00:12:52 - 00:17:36)
Continuity mistake: When the McCallister family arrive at the Florida flight and give in their boarding passes, Sondra is 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)
Continuity mistake: When Kevin is in the taxi going over the bridge, he is wearing gloves. But in the closer shot he is not wearing gloves. (00:19:30)
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 Kevin throws a rock through the front window of Duncan's Toy Chest, the alarm sounds and Harry and Marv run out of the store. In the next shot, the alarm that could be heard has mysteriously stopped. (01:17:39)
Factual error: When Harry and Marv arrive for the first time at Kevin's "funhouse", they look up to the roof and spot Kevin taking a Polaroid of them. The flash brightly illuminates them both, but the building looks to be at least 30 feet high; a basic Polaroid camera does not have a flash strong enough to reach such a distance (plus the street is already illuminated by lamps and Christmas lights). (01:23:05)
Other mistake: When the McCallister family is in the Chicago airport and Kevin is changing his batteries, on the P.A it says that American Airline flight 226 to New York is in the final boarding process, and Kevin runs after the man who is running to the gate. Once they are on the plane, the flight attendant announces, "Welcome aboard American Airlines flight 176 non stop service to New York." These are different flight numbers. (01:26:00 - 01:40:00)
Continuity mistake: In the first film, it is mentioned several times that Kevin is 8 years old. However, in this film it is stated that he is 10. When his parents are in the Miami airport security office, they say that he was left alone last Christmas. That would make him 9. Both films take place the same days, from about three days before Christmas until Christmas morning, so even if Kevin is born around Christmas time this is still a mistake.
Other mistake: In the scene where Kevin is making the hotel reservation on the phone, the lady does not even ask the dates of when he will be arriving and leaving the Plaza.
Factual error: No airport in NYC has the view of the New York City skyline that Kevin has when he realizes that his family is in Florida and he's in New York.
Audio problem: When Kevin plays the tape of his Uncle Frank singing in the shower, it starts with "We know a guy that can really do the cool jerk" twice. Yet, when he first tapes his Uncle, he doesn't start the recording until after that has been sung. The recording also sounds very clear. When he tapes him the door is closed, but the tape sounds the same throughout. Also, when his Uncle says he's gonna "slap him silly" Kevin shuts the door behind him and you can hear it shut. On the tape there is no sound of the door shutting.
Revealing mistake: When Tim Curry runs out of Kevin's hotel room after being scared by the inflatable clown doll he hits his knee on a table. When he hits the table and then hops away you can clearly see that he is wearing a knee-pad.
Other mistake: When Kevin first enters the hotel, he is told to get to the lobby he should go straight ahead and turn left. The next shot shows him turning right into the lobby.
Continuity mistake: When Kevin is running away from Harry and Marv he buys strings of pearl necklaces, and pulls them apart on an icy corner. When the bandits slip on them, there are more pearls there than Kevin dropped.
Factual error: When Kevin goes in the limo, the front desk manager attempts to process a charge on the credit card, which comes back as "stolen." No credit card terminal flashes "stolen" when a credit card has been compromised or cancelled. The machine would simply decline the transaction, much like if the credit limit had been exceeded, or tell the merchant to phone for authorization.
Factual error: The picture that Kevin takes of Marv and Harry through the toystore window is perfectly clear. There is no way you can take a picture of something through a window without the flash reflecting back and ruining the image, especially from as close a range as Kevin was.
Continuity mistake: When Kevin is first watching the movie in the hotel room the room service guy already has two scoops of ice cream in the dish and is putting in a third. Then later in the scene the guy asks, "Two scoops, sir?" and only one scoop is in the dish and is just putting the second scoop in.
Other mistake: When Kevin jumps off the hotel loading dock, Harry has his hands up. This displays the 'M' burnt into Harry's palm in the first movie. The 'M' should have been sideways because he grabbed the hot door knob at 90° in the first film. Same mistake is in the first film.
Visible crew/equipment: In the scene where Kevin lights the rope on fire, he turns to run away. Watch the window he passes, there is a crew member standing there with his arms folded watching.
Continuity mistake: In the scene where Harry and Marv are at the skating rink, the front of Marv's hair is constantly changing from shot to shot. It's either poofy or pulled back due to the earmuffs he's wearing.
Answer: He's heading back to the hotel most likely to apologize for spending such a huge amount.