Theories

- There are also considerable differences in design between the Assault Trooper/Assault Captain and the Assault Enforcer, such as differing head shapes and the Assault Enforcer having white claws.

• The enemies are designed to look fearsome, and there are only so many ways to achieve this (particularly in sprites of such low resolution). They are also intended to look distinctly alien, and again this can only be comfortably achieved in just a few ways. A similarity in their appearances may just be coincidental.

• These creatures are both part of the "Assault" group.

- That title almost certainly has nothing to do with their genetic relationships, and is likely just a descriptor of what role they play in the invasion of Earth (the "Assault" aliens being those that launch attacks and forcibly expand the alien territory). Further, most enemies have names that are solely descriptive of what they do (e.g. the Protector Drone protects the Alien Queen), which is even more evidence that the names of the aliens is just a descriptor rather than a genus.

- Their appearances are also somewhat different, most notably that the Overlord has legs while the Assault Commander doesn't (or at least, no visible ones). The Assault Commander is also fat, whereas the Overlord is big and muscular.

• These differences could be a result of preferential treatment (an alien designated to become an Overlord may be given more physical training and drugs to become stronger). However, this is entirely speculative, since we know nothing of alien breeding methods.

• It could simply be a coincidence, due to the artistic difficulties of designing visually unique aliens. If so, similar appearances would mean nothing.

+ They both use explosive projectiles (rockets) as their primary attack method.

• This may mean nothing; there are only so many ways to attack in the game.

• They are both first introduced in the same episode (Lunar Apocalypse).

- This could be coincidence. Both of these creatures seem like they belong in the places they are both found in (often dank dark places, and underwater).

+ Protozoid Slimers appear to have large brains inside them, just like an Octabrain does. Also, they both have tentacles (of a sort) and large mouths).

- Of course, there are many differences between their appearances too, such as their colour.

• Large mouths can be explained away by noting that all organic enemies have large mouths - this could just be so that they appear threatening. Also, the Protozoid Slimer having a large brain can be explained by reasoning that any sufficiently large organism (even a relatively simple slime monster) must need some kind of brain in order to live at all.

+ Protozoid Slimers have eight tendrils (can be seen once one is latched to Duke's face), as do Octabrains.

• Limitations in the games could be the reason why all these spawnings happen in the same way.

• There is footage in the 2001 trailer for Duke Nukem Forever showing people with long tendrils spewing from their bodies. These tendrils could belong to developing Octabrains inside their bodies.

• We don't know if anything from that trailer is still relevant now.

+ At the beginning of the episode The Birth, a group of Protector Drones can be seen surrounding a woman who is about to give birth (it is implied that the offspring is the Alien Queen).

- This is a different species. Just because Protector Drones do it, doesn't mean Octabrains do. Also, the Alien Queen can spawn Protector Drones without the need of human hosts.

• This is a different species. Octabrains may always require host bodies, as opposed to the Protector Drones that just need a host body to give birth to an Alien Queen.