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? (00:20:10 - 00:38:55)
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. (00:03:25)
Continuity mistake: When Sid wakes up and finds out that his family has abandoned him again, a animal in the process of migrating is walking by him leaving no traces of anything. But when Sid takes his next step, he walks into some feces he claims belongs to the animal that just walked by him. But the animal did nothing at all, the feces wasn't even there to begin with. (00:05:59)
Continuity mistake: When Sid is climbing up the wall, he is having trouble at a metre above the ground, Manny starts to say something. Mid-sentence the shot goes back to Sid and he is twenty metres up. (00:20:35)
Continuity mistake: When the Sabres are chasing Sid on the skis (made out of two slabs of rock), Sid loses one of the skis, one of his feet is then flapping about and the other one is on the back end of the ski (which then becomes a snowboard). In the next shot(no time between them) Sid has his foot halfway up the ski.
Continuity mistake: In the cave scene where the animals are racing down ice tracks, there is a close shot showing Manny with his trunk flapping to his right. Then there is a long shot and his trunk in now flapping at his left. (00:47:10)
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.Bradley Bing
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.