Corrected entry: In the scene where the newspaper shows Alex being rescued from his crate, the date is April 8, 1972. During this time, if you look in the background during several shots, you can see the World Trade Center. The World Trade Center 2 was not completed until 1973.
Corrected entry: Alex is dancing as he is fighting Teetsi. Makunga is shown saying "this is even better than I thought." The lion behind him (in the crowd) in the same scene is also seen mouthing the line at the same time.
Correction: He isn't mouthing Makunga's words. He is whispering something to the lioness beside him but he is not mouthing Makunga's line. He isn't heard because he speaks silently. The fact that he speaks his line while Makunga speaks his is purely coincidental. This entry is based on the opinion, not on the fact.
Corrected entry: The movie was made in 2008, but the Twin Towers appear in the skyline of NYC when Alex arrives.
Correction: The part that shows Alex arriving in NYC is a flashback. Presumably prior to 2001 since he's a cub.
Corrected entry: When the old lady kicks Alex out of the jeep, Alex takes her handbag. The handbag is with the old lady again in several scenes after that.
Correction: No mistake. Another tour members hands it back to her and says he found it in the scene after the penguins steal the jeep.
Corrected entry: When little Alex is in the box in New York, there is a fish in his hand when he is taken out of the box. The box is sealed tight when he is seen floating from Africa and to New York.
Correction: No, there is a hole in the box, as shown from a cutaway of little Alex curled in the box, out to the open sea.
Correction: No really a mistake. The exterior of the buildings were completed long before 1973 so it is possible to see the towers as he entered the harbor.