Bad facial animation.
I enjoyed this movie a lot and while a lot of the animation was simply superb, I was very disappointed with the way the facial expressions of the characters were animated. They were too static, too plain. Whether a person is really angry, or really happy, their facial expressions changed very little.
For anyone who is familiar with the comics knows that the characters in it, despite having a dot for an eye, had brilliant expressions. One could easily tell if Tintin was happy or puzzled or sleepy. In this movie, everybody seems to have the same look on their face for most of the movie.
Mr McGee, don't make me angry. You wouldn't like me when I'm angry!