Revealing mistake: In the beginning when Nick gets a present from Fred you see that the background is fake.
Revealing mistake: After the old lady steals the meteor rock from Luigi, the big lady in red picks her up and throws her off down below into a moving car. She gets up and shocks the driver, causing the car to rear end the vehicle in front of it. If you watch closely, you see the engine top shift forward and the back of it lifts up. This reveals it is just a fake prop attached to the vehicle and not a real engine.
Revealing mistake: There are no keys in the ignition when Mike is driving the white truck.
Revealing mistake: Sam is supposedly far away from civilization, but throughout the movie you can see a ski slope in the background. (00:16:05)
Revealing mistake: During "Our Beginning," True Heart Bear takes a walk beneath the ship's deck to check on the sleeping cubs. But when Proud Heart Cat wakes up for a moment, his tummy symbol is visible - which he's not supposed to receive until arriving at the Kingdom of Caring several minutes later. (00:02:20)
Revealing mistake: When the prisoners commandeer the balloon and proceed to take flight, you can see a television antenna on one of the buildings in the background. (00:07:20 - 00:08:00)
Revealing mistake: During the opening musical number, right before Gary joins the large group of people for the dance, he accidentally kicks Walter out of frame. Watch closely though. His foot comes nowhere near Walter when he supposedly "kicks" him.
Revealing mistake: When Maleficent freezes the people in the church, the actors can't help moving.
Revealing mistake: When Helvetica is on the rocket bike, her hair doesn't move.
Revealing mistake: Casper is shown tying together the shoelaces of the students in Kat's class. When the bell rings and class ends they all get up and fall down. If you look closely you can see that their shoelaces are not tied together.
Revealing mistake: When Mombi's headless body wakes up and begins to walk towards Dorothy, you can see a black, blurry haze around her neck in two shots, where an effect was used to remove it.
Revealing mistake: When the cats are driving Mr Mason into the factory you can see skid marks on the ground from previous takes. (00:51:30)
Revealing mistake: During the song "Remains of the Day", at one point, towards the end of the song, you can see metal wires in Bone-Jangle's wrists, revealing how the stop-motion character was kept together.
Revealing mistake: The first morning, when Robert takes Giselle to work, they enter atrium of the Time Warner Center (the well-known statue of the female Giselle admires is one of a set, the other is male), which is located at 8th Ave and Broadway, at the southwest corner of Central Park. Upstairs, when Sam tells Robert that she can't find where Giselle is from, and then when Giselle speaks to Phoebe, the very distinctive Johnson Lipstick Building (it's reddish and has three receding oval-shaped levels) at 53rd and 3rd is seen outside the window. The office scene is obviously not filmed at Time Warner, because it's impossible to be in an office at 8th and Broadway, on the West Side, and be next door to a building located at 53rd and 3rd, on the East Side. (00:35:40 - 00:40:35)
Revealing mistake: When Mia meets Asana at her birthday party and asks what she's been up to, Asana replies "oh, partying girl" with a British accent. Then when Asana is talking about Prince Jaques, the accent is gone. Then, at the slumber party, her accent slightly returns.
Revealing mistake: When Scrat removes the giant acorn in Scratlantis the city is immediately flooded. Everyone in the background is blown away by the sudden rush of water. However, both Scrat in the background and Scrat's host (slightly off-camera) in the foreground don't move and don't seem to be affected by extremely strong flow. (01:18:50)
Revealing mistake: When the Chairman is watching the TV screen where Damien Drake is being interrogated, the man steps in front of the screen and says "he's about to crack," then he walks backwards as if being pulled, but you can tell the moment Damien puts his legs around him, after several steps. So what pulled him back?
Revealing mistake: During the scene when Hawkins is in the jousting tournament, Griswald takes a swing with his mace and apparently smashes Hawkins' head (inside his helmet) off. Then the horse Hawkins was riding stops, and he extends his head from inside his suit of armor and smiles. Watch carefully throughout this shot - Hawkins' hair/the back of his head can be seen past the edge of the armor where the hole for his neck should be.
Revealing mistake: When Ed and Dexter are in the ventilation shaft, watch when they fall in the trolley thing. If you look carefully you can see Ed's wig hanging on the edge. It's got a good burger hat on it.
Revealing mistake: When the dragon is hatching, a light bulb is visible just behind and to the left of her egg. (00:14:10)
Suggested correction: What appears to be a light bulb in the wide shot is actually a leather strap attached to a larger leather item. This can be seen more easily in the close up shot in the moment after the egg fully breaks.