Goofs

In the ice cave, Sid turns around a bend, looks right (heaves a sigh of relief), and then looks left to find the scary fish fossil. Then he turns right and immediately sees the dinosaur fossil. There was no dividing wall or corner between the 2 fossils, so the dinosaur should have been visible to Sid even before he saw the fish.

During the fight with the dodos, Diego disappears when Manfred is keeping the melon away from the dodos. When the melon goes flying, Diego is back beside Manfred.

During the sliding scene, Manny slides through some spikes on a slab of ice right after Roshan, who, weirdly enough, got through it unharmed.

When Soto describes his plan for bringing down the mammoth, Zeke and Oscar swap positions between shots.

In the first shot of the human camp, the camp is on the left side of the river that leads to the waterfall. During the tiger attack, the camp switches places to the right (note where the baby's mother jumps).

While escaping from the lava, Manny at one point makes a jump to get over a chasm. Elephants (and by extension, mammoths) are of the few mammals that can't jump.

When Scrat's coconut falls from the tree, it has already had its husk removed. The directors acknowledged this on the DVD commentary. They may have been worried that a lot of their audience would not recognize a coconut with its husk on.

The first animal to step on Scrat in the opening is a mammoth, yet no mammoth is visible in the long shot of the crowds of animals. In fact, no mammoth other than Manfred is seen throughout the sequence. With this, a large bird also steps on Scrat, but no birds are seen in the crowds. We also only see two legs of each animal stepping on Scrat even though three of them are quadrupeds.

Just before Sid comments that his "feet are sweating" there is an overhead shot of all three main characters walking along the snow. Their feet are moving but their bodies are moving forward far faster than their steps would take them and they appear to be sliding forward on the snow.

When the sabertooth pack is chasing Sid and he "skis" away, Sid is kicking up powder and leaving tracks in the snow, but during the early stages of the chase, his pursuers are running across the top of the snow leaving no tracks.

In the rain scene, when Sid asks Manny "So what about you? You have family?", Manny turns away from Sid. The camera is on Sid in this duration, so we don't get to see Manny turning. The shelter is so small and snug, it should be impossible for a mammoth to turn around without first coming out.

When Manny tells Sid, "I don't care who started it, I'll finish it!", there is a noticeable jump in audio mid-sentence, indicating that the line was (poorly) edited in order to fit Manny's lip movements.

Animals, from many different epochs and continents, mingle in 10,000 B.C. North America.

The humans seen in this film are described as Neanderthals. However, Neanderthal specimens were found in Europe and parts of western and central Asia, not in North America.

In one scene, the Stonehenge monument is seen, covered in snow. However, Stonehenge is believed of being constructed from from 3000 BC to 2000 BC, thousands of years after the events of the movie which is mainly set around 20,000 BC.

When Sid tries to escape from Diego's jaws after faking his death and screams "Manny! Manny!", his lips don't match up. This is because the scene was originally animated as Sid trying to get rid of Sylvia (who's scenes were ultimately cut from the final film) and he screams "Sylvia! Sylvia!". The scene was later revised as Sid escaping from the rhinos and his dialogue was re-recorded, but his lip movements were not re-animated.

At the start of the cave drawings scene, the baby babbles, but his mouth doesn't move.

When Manny is on the falling ice slab after he rescued Diego, Sid shouts "Manny!", but his lip movements indicate he originally said "Raymond!"

During the avalanche scene, Scrat runs through a field and in between two glaciers. When he breaks free, he begins to free fall from several miles in the air.

When Diego is chasing the baby and his mother, he runs through the river with no hesitation or fear of the water. In Ice Age: The Meltdown (2006), until near the end of the movie, Diego won't go into the water or quickly exits if he gets his feet wet.

When Zeke is fantasizing how to butcher Manny, he notes separating the white meat from the dark meat. A mammoth isn't poultry, which means the classification of dark vs. white meat doesn't apply.

In the very beginning, Manny's feet are seen following the crowd. Seconds later, he is going in the opposite direction.