The Aliens In ‘Prometheus’ Are ‘Alien’ Aliens, But Not Exactly?
These reports are based on rumors from "reliable" sources, so don't go hopping aboard the Nostromo just yet. What I'm hearing is that these are Xenomorphs, just in a different form than we're used to:
Remember how the alien took on canine qualities after gestating in a dog? You may even suppose that the first film’s alien was so recognisably humanoid because it had grown in a human. The same applies here: generation by generation, the creature mutates. As Prometheus begins, the xenomorph is not too recognisable. Sure, it has that alien DNA that Scott and Fassbender teasingly referred to, but it’s missing… well, it’s missing human DNA. Or dog DNA.
All you have to do is imagine how it might look if it were to mix DNA with another alien species… and I think we’re starting to work it all out.
This strikes me as a very 2009 Star Trek-ish workaround for including Prometheus in the Alien universe without having to deal much at all with established continuity. These aliens will look like anybody they're grown inside, which could be tentacled octo-monsters, Cloverfields or mutant turtles, and the film may take place on the other side of the same galaxy as Ripley and friends. Problem solved.
Oh, and the title might not be Prometheus at all. Based on this info, may I humbly suggest, Quasi-Alien: The Porcupine-Aliens Strike. (/Film, Bleeding Cool)