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They had no idea how to end the movie - that's when they called me in to try to resolve a dispute. The key issue was how to portray extraterrestrials that would surely be encountered at the end when they go through the Star Gate. Kubrick was arguing that the extraterrestrials would look like humans with some slight differences, maybe à la Mr. Spock (Ed. note: like Clindar). And Arthur was arguing, quite properly on general evolutionary grounds, that they would look nothing like us. So I tried to adjudicate as they asked. I said it would be a disaster to portray the extraterrestrials. What ought to be done is to suggest them. I argued that the number of individually unlikely events in the evolutionary history of man was so great that nothing like us is ever likely to evolve anywhere else in the universe. I suggested that any explicit representation of an advanced extraterrestrial being was bound to have at least an element of falseness about it and that the best solution would be to suggest rather than explicitly to display the extraterrestrials. What struck me most is that they were in production (some of the special effects, at least) and still had no idea how the movie would end. Kubrick's preference had one distinct advantage, an economic one: He could call up Central Casting and ask for twenty extraterrestrials. With a little makeup, he would have his problem solved. The alternative portrayal of extraterrestrials, whatever it was, was bound to be expensive.

- Carl Sagan