Much like George Lucas' THX-1138, Dark Star had its beginnings as a film school project which was later expanded into a full-length movie with the help of later investors. However, while Lucas became far less serious when he started working with big budgets, the opposite phenonmenon occured with Dark Star's creators Dan O'Bannon (later scripter of such hits as Alien and The Abyss) and John Carpenter (later director of such hits as The Thing and Halloween). In fact, Dark Star often seems to make fun of elements found in Carpenter and O'Bannon's later works, as if they knew what directions they would later be taking and decided to parody themselves before anyone else got the chance. For example, there's an alien that looks like a blown-up beachball bouncing around the ship and causing trouble, providing a very silly alternative to the insect in Alien. Of course, other classics are billiantly parodied in this movie as well, especially 2001 with its out of control, intelligent computer and in the scene of astronauts floating off into space.
Much like Monty Python, the humour works on many levels. In addition to slapstick, you get rather intelligent and philosophical humour. Not all of it works, but there are enough hits to make up for all the misses.
Given the original budget of the film, don't expect a visual spectacular. Comparing Dark Star to the creators' later works is like comparing Lord of the Rings to Peter Jackson's first film, Bad Taste. This first film has a sort of roughness and lack of polish to it which really emphasizes its moments of brilliance. Too bad the film isn't longer.