We are told its structural perfection is matched only by its hostility and a habit of shedding its cells and replacing them with polarized silicon, vies it a prolonged resistance to adverse conditions. But theories of the alien's physical and mental attributes don't stop there...

IT'S A HERMAPHRODITE: Scott considered the creature to be sexless -- contradicting Ash referring to it as a 'he,' Dan O'Bannon's cut pyramid sequence citing two sexes, and the Mother in Aliens. 'The creature emerged from the logic of how it could reproduce itself,' says Scott. 'Therefore I guess the alien is a hermaphrodite.'

IT'S A HYBRID: As part of the alien's adaptive process, it reproduced characteristics of its host -- thus the alien we see has a humanoid form. (In Alien3 it bursts from a dog, and runs on all fours.) 'The alien on the Nostromo had the characteristics of the Space Jockey and Kane,' says Scott. Do we know what it looks like at all?

IT'S A ROGUE: O'Bannon had a theory that the adult alien roaming the Nostromo wasn't typical of its species. 'It's never been subject to its own culture,' he explained; 'it's never been subject to anything except a few hours in the hold of the ship. Quite literally, it doesn't have an education. The alien is not only savage, it is also ignorant.'

By Aliens, the creatures show distinct wit -- for instance, how they access the barricaded lab via roof space. Even in Alien, the creature shows a willfulness: how else to explain why it got onboard the Narcissus? The alarm bells were sounding and it figured out the Nostromo was about to blow.

IT WAS DYING: 'Like a butterfly, it has a very limited life span in which to reproduce itself, 'says Scott, contending the aliens lived as briefly as four days. 'That's why it didn't attack Ripley on the Narcissus. It had found a protective corner of the ship and was working itself in there to die.'