Deliberate mistake: The position of the head of Kim Jong Il's statue changes during the scene. (First time we see the statue in this movie, it's blinking and moving: it is a real person). (01:14:45)
Deliberate mistake: At the very end of Gary's motorcycle ride, the marionette has been replaced with a stunt dummy. He's very up-right, like a Ken doll, and has no stubble on his face.
Answer: I read an interview with Trey Parker and Matt Stone where they said that they had not intended for it to be that way but that when they made the Matt Damon puppet, it looked so retarded that they thought it would be funny to just have him be retarded in the movie and only say his name. They said it was nothing personal against Matt Damon.