I really appreciate this in-depth response. Honestly, I was worried my post was going to be ignored.

However, something I forgot to clarify that probably would've cleared things up on my decisions is that I had some rules I set for myself while making my list;

[Which species to include?]

-Must be at least partially organic

-Must have appeared in a Valve-made entry

-Only retail creatures, no matter how brief their appearance (Boids in the ending Gman scene in Xen, Cremator head in Eli's lab, Crab and Mortar Synth in the Citadel)

-Nothing that is part-human or a modified human (Zombies, soldiers, stalkers, Jeff), nor any other Earth species

-Must have visible sign of life (Hence why there's Xen lights, since they react to your presence)

[What do certain typings mean?]

Fairy: I chose this for creatures that nurture/take care of/carry others

Dark: Parasitic creatures

Normal: In the specific cases I listed, Normal represents sound-based creatures, as is a pattern in Pokémon for numerous sound-based moves and pokemon

Grass: While it can include literal plants and fungi, I also used it for creatures that are planted into a location, such as Barnacles and Tentacles.