Continuity mistake: Right after Alex and Beta have their argument in Alex's Bedroom, Louis wakes up and then pretends to fall back asleep. In the shot (with the door that Alex just used in the background) Louis gets up again and bends over to look at Beta, he's moving towards the camera. However, in the next shot, Beta hasn't moved, and he was looking in the direction of Alex (the opposite side of the bed Louis should have been on).
Trivia: In the scene where Alex first meets Centari and climbs into the Starcar, notice how Alex's hair looks natural as he stands outside the car. After he gets in and asks "What are you doing?", notice how his hair looks totally different, almost as if it is burnt or something. The actor had become very ill and had to shoot certain scenes after he got sick. He wore a wig, which explains why during certain parts of the film, he looks pale and his hair looks burnt. You can also notice the wig in the scene when the "Beta" unit rides in a truck and laughs his head off to have a good time.