Factual error: In the scene right after pinback shoots the beach-ball alien, we see the Dark Star space craft cruising past a planet with a sun in the background. You can see a reflection on the planet which is coming from the space craft. I'm sorry, but usually ships in space are not large enough to reflect off a planet, especially to the degree this one does. (00:48:20)
Revealing mistake: In the main control room / flight deck, the illuminated buttons are clearly top-down plastic ice trays.