Revealing: In the main control room / flight deck, the illuminated buttons are clearly top-down plastic ice trays.

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.

Continuity: As Pinback puts the fruit down in front of the alien, its feet and spots change position.

Revealing: When Pinback is hanging from the lift, just before he decides to undo the bolts, you can see a piece of wood supporting his back.

Revealing: When Talby is mending the communications laser, in one shot the laser beams are not there. The sound effect is audible and there are two white strings visible where the laser should be.

Continuity: When the alien attacks Pinback, he drops his broom in the middle of the room. There is then an overhead shot which shows it back in the corner.