See how smart it is.' ― Aaron and Ripley (from Alien 3) ' You really wanna bet this thing's that smart?'

Furthermore, the Special Edition Chestburster is considerably larger than a typical specimen when it finally emerges from the corpse, indicating it had already begun maturing within. However, in the Special Edition, where the Alien is spawned from an ox, it is hinted that this could be a result of the Chestburster being unable to escape its host's chest cavity at the typical interval (likely due to its higher structural rigidity), as the ox dies some time before the Chestburster hatches. Why this is so is never explicitly stated. Unlike other Chestbursters, in Alien 3 the Runner is shown to be born nearly fully formed and only needs to grow larger. They can also run into prey with crushing speed and weight. A Runner also tends to use its tail attack (which stuns the victim) more often than the Drone. However, physically Runners are not as tough as Drones, relying on their speed and agility to outmaneuver threats rather than strength to overcome them. They are equally capable of traversing floors, walls and ceilings at speed on all fours. While capable of standing and walking on their hind legs, Runners typically remain in their quadrupedal stance when moving and this makes them among the fastest Xenomorphs. Their skin is tinted brownish-red as opposed to the more usual grey-black.

They also have a more barrel-shaped chest, similar to many quadrupedal animals. Like Drones, Runners have smooth domed carapaces, and they are also one of the few Xenomorphs not to have the distinctive dorsal tubes typical of many other castes. In the case of the Runner, the adult has most notably taken on its host's quadruped posture, with digitigrade hind legs. Runners are physically quite different to human-spawned Xenomorphs due to the species' tendency to 'inherit' aspects of its host's physiology through the DNA reflex.

Cat attacks runner?