The Beluga-Xenomorph, also known as the "Holloway Alien" after its host, was a Xenomorph creature cut from Prometheus early in its production. In Jon Spaihts' original script, titled Alien: Engineers, the creature stalked and killed several crew members of the Magellan. Its role was entirely written out of the finished film.
After Holloway is attacked and impregnated by an Octo-Facehugger inside the Engineer structure on LV-426, he is found and rescued by Jocelyn Watts. The two return to the Magellan and make love, but as this happens the Beluga-Xenomorph emerges from Holloway, killing him. It attempts to attack Watts, but is forced to flee when several other members of the Magellan's crew intervene.
The infant creature escapes into the bowels of the ship, where it rapidly grows and begins killing the crew who are searching for it. It later attacks Janek on the bridge as he and Watts attempt to stop the Juggernaut leaving LV-426 with its cargo of Xenomorph Eggs, although Watts is able to kill it with a sub-machine gun.
Unlike other Xenomorphs, which are encased in rigid, black exoskeletons, the Beluga-Xenomorph is described as being ivory white and boneless, the latter of which allows it to alter its body shape and become a gelatinous, amorphous blob, allowing it to squeeze through gaps that would otherwise be too small for it. Its skin is vaguely translucent, and at the front of its elongated skull, a human-like skull can be seen beneath. It has long, spindly limbs, and jaws that can lever forwards out of its mouth (a trait given to the Deacon in Prometheus).
- The Octo-Facehuggers from which the Beluga-Xenomorphs are created are implied in Spaihts' script to be the 'original' form of the Xenomorph, while the Facehuggers seen in the earlier films (and later in the script) are a 'weaponized' version of it, modified and improved by the Engineers. This in turn implies the Beluga-Xenomorph is the original form of the Xenomorph adult.
- The Beluga-Xenomorph's ability to alter its shape and pass through small openings mirrors the ability of the "Rogue Alien" in David Twohy's script for Alien3, which could realign its exoskeleton to pass through narrow gaps.