Revealing mistake: When the canoe is speeding down the hill, there's one scene where you can see there's already a groove in the snow from where they did a previous take.
Revealing mistake: During the scene in the bow thruster room near the end of the movie, Richard Dreyfuss rushes to the thruster tunnel access hatch to open it. As he grabs hold of the wheel, the hatch and frame visibly move, exposing it as the lightly built set that it is.
Revealing mistake: Just after Boog breaks the dam and the deer herd is bounding across the dry riverbed, at the moment they realize they are going to be swept downstream by the wall of water, their legs disappear - just left out of the animation cell. Very obvious; no slow-mo needed to see.
Revealing mistake: The infant baby was computer animated in every scene in which the face appeared. Even the feet were obviously touched up by computer in the hallway scene. The lighting isn't quite right, the skin texture isn't quite right, and the child's face is just too animated.
Revealing mistake: When David Arquette is preparing to drive his rocket car, he does a u-turn to get pointed in the correct direction (towards his friend who is filming). The image is reversed at that point, so that he appears to be driving from the passenger side of the car.
Revealing mistake: When Stella the skunk yells at the cat, she pokes him on the face. However, you will notice that the hand looks a lot like a human hand, not Stella's.