Revealing mistake: When Alex says they should go find the penguins, he says "To home" and Marty, Melman, Gloria and Julien place their hands on top of his hand. In the next shot it shows all of them together. But due to the position of Julien and his arm length, it would have been impossible for Julien to have his hand fully placed on Alex's hand. (00:05:05)
Revealing mistake: When Aladeen tries to jump the fence of the UN, a hearing device is seen in actor Sacha Baron Coen's ear.
Revealing mistake: When Ralph returns to the penthouse after destroying Vanellope's kart, he goes out onto the balcony and we can see the corner of the 'OUT OF ORDER' sign reflected on the window to Ralph's left. The piece of tape is missing in the reflection.
Revealing mistake: At Coney Island, K zaps J's neck with a tazer and knocks him out. J is seen falling onto his back on the ground, where the background fades out to show time passage that he wakes up sitting in a chair in MiB head quarters. The effect was cool, but the way it was done reveals itself. J wakes up in a leaning back seated position looking up as his head is slumped back over the chair. It is obvious they used this part of the footage to show him lying flat on his back on the ground at Coney Island, only you can tell he is not lying flat on his back. (00:42:55)
Revealing mistake: In the opening shot, when it pans towards Mr. Leonard and the old lady, the street lamp that is positioned to the right of Mr. Leonard's car begins to pass in front of the car even though it is placed on the other side of it. (00:00:20)
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: In the scene where "More Than Words/Heaven" is sung, there is a montage of shots of Drew playing guitar on stage and Sherrie singing outside. One of the shots of Drew has been horizontally flipped - in it he's now playing guitar left-handed and his "The Bourbon Room" T-shirt has the logo back-to-front.
Revealing mistake: When Sparky's tail pops off there is a hole where it popped off. But when the tail goes into the bucket the hole is gone.
Revealing mistake: In some of the shots where Greg is in the pool with no swimsuit on, you can see that he is wearing shorts in it before he asks the girl to give his swimsuit.
Revealing mistake: When Curtis or Catherine are driving while it is snowing (e.g, on their way to the Christmas party), there is relatively heavy snow going horizontally past the side windows but there is no indication that "snow" is falling on the windshield. Wipers can't be heard (like one would expect driving in these conditions) and there is no dimming of light inside to suggest the heavy snow is blocking some light. Also, the way the snow is accumulating around the side windows is not typical. (00:33:04)
Revealing mistake: When Cam punches the dog, you can tell that the footage was sped up.
Revealing mistake: In the flashback of four years ago to the night that John met Lori, when he accidentally pushes her to the floor, it is a dummy that hits the floor.
Revealing mistake: When FDR jumps in the Beetle to help Lauren you can see it's a stunt making the jump - his hair is darker.
Revealing mistake: Lazy prop department at work in the opening credits of this movie; look at the guest list. The second page and the first page are an exact copy and paste of the same names and addresses. (00:01:35)
Revealing mistake: When the arrow Larry shot into the sky comes back down, it pierces Mac's thigh and into a thick pad which can be seen under his pants.
Revealing mistake: When Ray reminisces about having fought the Germans in WW2, a flashback is shown with him fighting in a bunker. He is carrying a No.4 Lee-Enfield rifle which requires the bolt to be worked after every shot to reload. However, he is shown firing two shots in rapid succession without moving his hands at all, revealing the shots to just be flashes added after filming.
Revealing mistake: In the scene when Dodge is knocking at the second house to see if Olivia is home, check out the top left corner of the screen during the shot of Penny sitting in the car - a bird flies by inside the car. The only reasonable explanation is that the visual effects team not only made the bird graphic visible through the window but also in front of the rest of the car. They might have forgotten to bring the car layer in front of the bird layer, causing a bird to be seen flying over top of the entire image. (01:14:00)
Suggested correction: It's a reflection in the windshield.
Revealing mistake: When Sam first sets off in the canoe, it is obviously being towed because it leaves a moderate wake even though he is barely paddling.