Continuity: In the first 'Ice Age' Diego isn't afraid of water (in the beginning he chases the woman and the baby through the river before she jumps off the waterfall and never shows any fear) but in this one he suddenly is.

Other: Just after the valley floods, Manny is seen pushing a log to pry the rock out blocking Ellie's way out. You will notice that Manny is pushing it the wrong way.

Continuity: When the anteater is telling the kids to look at Manny because they'll probably never see another mammoth, you can see Manny's shadow on the ground and it's facing forward, but when the camera switches to facing Manny he's facing sideways.

Continuity: Near the very end of the movie, we see that Scrat's acrorn holes as he goes up the iceberg wall are in a fairly straight line. However, when the ice begins cracking, the cracks follow the line of holes which are now no longer in a straight line but very jagged.

Plot hole: At the end of the movie, when the water drains away, there would be no way for a) the amount of water to drain away that did and b) for the mammoths that came through to be completely dry.

Continuity: Right at the beginning of the movie, when Scrat is looking for his nut, there are no teeth marks where he stuck his teeth in to climb.

Continuity: In the scene where Scrat gets attacked/attacks the piranhas, the acorn gets swallowed by a piranha on the right, after all the fighting, Scrat jumps on a piranha on the lower left, which spits out the acorn.