Visible crew/equipment: When the Starcar lands for the second time, there is a shot where the car comes to a stop in front of the camera. In this shot, the wooden rafters of the sound stage can be seen. (Noted in the director's commentary).
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).
Audio problem: When Alex and Maggie are going back into space at the end, everyone moves back and they yell goodbye. You can hear Otis say goodbye, but his mouth does not move at all.
Deliberate mistake: At the end of the film, when Alex, Maggie and Grig take off in the Gunstar, the crowd of trailer park residents watching them leave backs into the covered portion of the restaurant, right next to the 'Starfighter' game cabinet, which is readily visible in the shot. Mrs. Rogan then wonders where her younger son, Louis, is. The shot changes to show Louis pulling a bench up to the 'Starfighter' game to play it as dust from the Gunstar liftoff kicks up next to him while he watches it fly. Yet the crowd is nowhere to be seen in the shot of Louis playing the game despite everyone being huddled right next to it on the patio (his mother was standing next to it and should be able to see him). Given the proximity of the crowd to the game a moment earlier, Louis wouldn't be able to play it, let alone put a bench next to it. It's clear the filmmakers chose the image of the younger kid aspiring to be like his brother by playing the game over the logic of where the game was in relation to the crowd.