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: It is barely credible that a young Victorian woman like Elena would even think about wearing a goatskin miniskirt - exposing her legs in those days would be akin to walking about topless nowadays. Even if she did those bright yellow cotton knickers - gleefully visible in the scene in the beehive - are in no way from the 1860s. Her pants are a hundred years ahead of their time.
Continuity mistake: Rumplestiltskin looks completely different in this movie than he did in the previous film Shrek The Third; Prince Charming momentarily talks to Rumplestiltskin in the tavern during the third film, and the character looks completely different, has a different voice and different demeanor.
Continuity mistake: As Buddy walks out into the street at the start of the movie when the cat is playing dead, you can see several parked cars on the street behind him. When the van backs up to 'catnap' buddy, there are no parked cars. Then as the van drives off again, there is a different bunch of parked cars in the street. (00:03:54)
Continuity mistake: There's an electrical outlet on the wall below the window (aligned with the window shade's loop) in Sid's room near the Megadork poster, but when Sid throws Woody to the floor and raises the shade (before he scorches Woody's forehead with the magnifying glass), that outlet has vanished.
Factual error: Trevor - a Professor of Geology - boasts about having an article published in Scientific American, and that is not something any scientist would do. Scientific American is looked upon with slight disdain by the scientific community, considered to be a populist crowd pleaser. It is not even peer reviewed. Considering that he has just turned the geological and archaeological worlds on their heads he would have been better off publishing in Journal of Geological Research or Geology, both prestigious professional journals.
Visible crew/equipment: When Pee Wee is chaining up his beloved bike you can see the long chain coming up through the bottom of the bike box. Full screen version only. (00:13:40)
Continuity mistake: In the exterior front shots of Elliott's house there are some significant changes to the landscape in different shots. For instance, the two lampposts at the bottom of the driveway change to an entirely different style in some shots, and the huge garden boulders repeatedly vanish and reappear. Also, note when Michael takes off on Elliott's bike to go search for ET, the in-ground lamppost that should be beside the mailbox has vanished, but it reappears when all the government agents are setting things up outside the house.
Other mistake: When Adam comes in and says "when I woke up this morning, the pain was gone", Connie is mouthing his lines behind him.
Continuity mistake: After Mark is found, he runs into Kate's arms and hugs her and her sunglasses fall off her head, but then in the very next shot they're back on her head perfectly. (01:24:50)
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.
Continuity mistake: During Andy's daydream at the beginning of the film, Mr. Potato Head has an eye patch over his left eye. When the daydream cuts back to reality we see that Andy has removed Mr. Potato Head's left eye to symbolize the eye patch. But when Andy's mum comes in with the video camera, his left eye is suddenly back in. (00:01:15 - 00:05:25)
Factual error: Though extremely modest on today's standards, the dress worn by Clara to the hoedown shows far too much cleavage for the time. No schoolteacher would ever wear a dress like that in the 1880s.
Continuity mistake: There is a scene where the Chipmunks and Chipettes are singing the song "Girls of Rock and Roll." In that scene, it shows the boys walking up the stairs together and from left to right the order is: Simon, Alvin & Theodore. The shot goes to the girls then back to the guys. The order of the guys has switched: (left to right) Theodore, Alvin & Simon.