Alright, Aliens. These things have two stages; one generation is the facehuggers that hatch from eggs, and the other is the queen that lays the eggs and bursts out of people's chests. Now the facehuggers are symbiotic; to replicate, they have to attach to a host organism (of a different species). Then their DNA combines with the host's DNA and absorbs some of the best traits, pretty much the way Darwin described it. We will assume, for the purposes of this essay (*snicker*), that the dual-stage thingy was an inherent characteristic of the species, though I can't understand how it could exist without another organism to bind with, and, if that was the case, then the whole binding thing was already a trait of the species.
ANYway, so these aliens have blood that is also a very powerful motherfucking thing called "molecular acid." This is worse than the stuff your parents used to do at primitive raves (called 'love-ins'). This acid is MOLECULAR. It has molecules, not just atoms. I wonder if, when they stole the acid blood (not merely acidic— the blood itself is an acid), if they all went, "Well, gee. GFG (good fucking game, for the lay person; it means 'well done!') on having already mixed DNA with those space aliens whose MOTHERFUCKING BODIES AND INTERNAL ORGANS could not be eaten by acid." Or maybe it was like a RPG (role-playing game, again), and they all went, "w00t! We found the space creatures with the bodies that can't be eaten by acid! Now we can go back to that planet in level four with the acid blood space critters!"
I feel like I forgot to close a parenthesis in there somewhere.