Continuity mistake: When Kevin goes to the grocery, he buys Tide detergent. While walking home, the two bags break, but no Tide detergent falls out.
Factual error: In circling over Washington Dulles, a plane would fly over several airports that they could land at with perfect communication, including Richmond, Baltimore, Andrews AFB, etc. Also, there is no communication from the airport to the plane but the plane would be in range of no fewer than 15 transmitting stations that could have relayed messages.
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: Clarence tells George that his brother died at the age of 9 because he wasn't there to save him from falling through the ice, but when you see the tomb stone, it shows Harry Bailey was born in 1911 and died in 1919. That would make Harry only 7 or 8 years old.
Continuity mistake: When Melinda Dillon breaks the lamp, it is broken into many pieces, but when Darren McGavin is gluing it back together it is now in much fewer and bigger broken pieces. Obviously different broken lamps were used.
Continuity mistake: The train that transports The Haynes Sisters and Wallace and Davis from Florida to Vermont is shown as being of the Atchison, Topeka and Santa Fe Railway in one sequence, and of the Southern Pacific Railroad in another. Neither railway ran on the east coast of the U.S.
Visible crew/equipment: When a gremlin attacks the Mum from a Christmas tree, and the tree falls on top of her, you can clearly see a member of the crew with eyeglasses, wearing a red shirt, standing behind the tree pushing it forward on top of her. (00:54:30)
Continuity mistake: During the scenes at her Mother's house, Kate's hair goes from blonde to REALLY blonde.
Continuity mistake: Just before Batman takes his mask off at the end, the black makeup around his eyes vanishes while the mask is still on. (01:48:20)
Other mistake: When Jack first arrives in Christmas Land he doesn't know what is falling from the sky (snow) but he somehow knows that the children are throwing snowballs.
Continuity mistake: When Apollo is getting ready to fight the Russian boxer, he comes out with white boxing gloves on. Sometime during the announcement of the fighters, the camera shows Rocky and Apollo standing in Apollo's corner. Apollo is jumping up and down while pointing with an ungloved and untaped hand, He is saying "I want you". The next time they show Apollo, he has his gloves on again. (00:26:55)
Revealing mistake: Riggs handcuffs himself to the depressed businessman. They jump off the building but they're not handcuffed to each other anymore. They used plastic cuffs which could separate during the stunt in case anything went wrong. They break just as they jump, so they grab each other's hands to stay in contact. After they land the cuffs are attached again. (00:31:00)
Factual error: During the opening credits, the show's copyright date is shown in Roman numerals as MCLXIV. In Arabic numbers, that's 1164 - it should have been MCMLXIV for 1964.
Plot hole: At the end of the film, we see Edward carving ice sculptures in his mansion. How did he get the ice up there? First of all, it takes place in a warm climate and I didn't see a freezer up there in the castle. He couldn't have gotten ice from town because firstly he had scissors for hands and couldn't have gripped the ice. And, even if by some miracle he could, he wouldn't be able to buy any from town because everyone in town but Kim was convinced that Edward was dead, she told everyone that they killed each other. And Kim didn't bring it to him because she told her granddaughter in the end that she never saw him again after that night. So where did he get that ice?
Continuity mistake: After the Grinch unscrews the light bulb in the town Christmas tree, all the lights in the town go dark and the Grinch starts to take off in his sled-thing. When they show a close up of him, the lights are on. Then a few seconds later, the lights are off again.
Factual error: In the scene where Clark is working on the lights the full moon is shown. This is December 14th according to the advent calendar. On December 24th when Santa's sleigh goes sailing over the moon, it is still full.
Revealing mistake: When Tim Allen startles Santa Clause and he falls off of the roof, Santa's foot kicks up a blanket that was used to look like some snow on the roof. (00:14:10)
Visible crew/equipment: In the first scene of the Christmas party when Takagi steps out of one the offices and greets a couple of his guests, the camera pans left to show the orchestra and other guests. A huge shadow of the camera and its operator is being shown on the back wall, then the stage light gets moved to light a different area and the shadow is gone. (00:02:20)
Continuity mistake: In one of the ice skating rink scenes, the camera looks at John Cusack and there is no snow falling. It then cuts to Kate Beckinsale and it is snowing heavily. (00:09:25)
Revealing mistake: When the driver is taking Amanda to the airport at the end, all the dials on the car are at zero, so obviously the car is not moving at all.