Continuity mistake: During the scenes at the Northern Water Tribe, there is a cut in the middle of Aang's lower lip that occasionally will disappear and reappear.
Continuity mistake: When Aang leaves the room where Zuko and Iroh test him for being the Avatar, he is not carrying his staff, but outside it is suddenly in his hand.
Answer: The TV show Americanized the pronunciations whereas the movie said them correctly.
The show is American, so with original characters you're allowed to say them how you want.