Other mistake: Even though it is snowing throughout much of the movie, none of the snow seems to stick to any of the characters' fur. Even during the fight scene when they are rolling around in it, they are never covered with white.
Continuity mistake: When the squirrel gets stuck between the 2 glaciers he gets stuck at the bottom of them, but then it shows him getting fired out of the top of them.
Plot hole: In the Ice Tunnel scene, Manny, Sid, and Diego come to a stop on the vertical block of ice. It breaks, and they slide through a 'field' of icicles sticking out of the ground. Their 'sled' is shaved down to nothing, indicating that the icicles are sharp. After going through the same tunnel as the baby, how did the baby make it through that field?
Continuity mistake: The scene where Scrat is trampled you see the feet of a camel-like animal and the feet of a mammoth. When the camera pans up, the mammoth is nowhere to be seen.
Continuity mistake: Near the beginning of the movie, when Sid decides to return the baby, he starts trying to climb up the cliff. The baby falls out of the little sleeping bag. After that, we never see it until it's used in the plan to escape the saber-toothed tigers. Animals don't have pockets, and I don't remember seeing anyone carrying it around, so where was the sleeping bag in between these two times?
Other mistake: The scene where Manny builds his shelter, he is bothered by what Sid is saying and turns around. The shelter that Manny has built is not large enough for him to turn around in it unless he walks out and turns around, which he does not do.
Continuity mistake: Scrat lands on the main road and is not stepped on for 16 seconds. During that time, not one animal passes by. Yet once he is stepped on, the animals pass by at 2 to 4 seconds each, and when the camera pulls back, you can see dozens of animals. Scrat should have been hit as soon as he landed.
Continuity mistake: 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.
Continuity mistake: When Lenny and Oscar witness Soto's death, they are standing next to each other. But, in the next shot where Manny looks at them, Oscar is standing further apart from Lenny. They stand next to each other in the next shot, but in the shot where they flee, they're standing apart from each other again.
Continuity mistake: At the beginning of the movie, the feet of two mammoths and a dodo bird can be crushing Scrat, but when the camera pulls away no mammoths or dodos can be seen in the herd.
Continuity mistake: Just after they have finished meeting Diego, Manny says to Sid, "Okay I'll help you return him, but promise me you'll leave me alone after that" and Sid says "Ok ok deal", but as he says "deal" the shot changes and they are further apart then they were before.
Continuity mistake: At the part where Sid, Manny and Diego are at the "shortcut" Sid says "I choose life" and walks out of the shadow of the glacier thingies. In the next shot, the shadow is completely gone.
Continuity mistake: When Sid is relaxing in the 'goo' and has it splattered on his face (no-one knows what it is), he wipes his face off with Manny's trunk, none disappearing. In the next shot, the 'goo' has completely disappeared from Sid and the baby.