While Kenai is falling of the ledge before he goes into the ice cave, his rope completely disappears.
When Rutt claims Koda as his new brother, he is sitting right next to him. But after Rutt and Tuke have their brotherly moment Koda is positioned farther away from both moose.
In the opening scene, the DVD subtitles identify the narrator as Sitka, when it is actually Denahi.
Mammoths have been extinct in North America before the last Ice Age ended, and the movie took place after the last Ice Age ended, so they shouldn't have appeared in the movie to begin with.
A spear isn't that strong to be able to make a glacier calve.
At the beginning of "On My Way", when Koda sings the last line of the first verse (before it transitions to Phil Collins singing), his mouth isn't moving at all.