When Don (Dieter Laser) is floating through the spaceship at the beginning of the movie, it is obvious that in the shots where Steve (Uwe Friedrichsen) and Dug (Claus Theo Gärtner) are visible in the background they are in reality hanging upside down with the camera turned 180 degrees to make it look like Don is weightless above them, because Dugs hair is standing up whereas in all other shots he has straight hair.
The image of Jupiter reflected in Don's helmet is not flipped as a reflection should be.