Yes, friends, Hydra was profoundly influenced by a giant robot anime. A particularly unusual giant robot anime, mind you. This series is one of my early memories of Strange aesthestics...
As a basic example, let me toss out Beta. Okay, let's look at two characters from the series.
Rei, extremely autistic, passive, will-less girl. She is a clone of the mother of the main character (Shinji). In fact, she is a massively copied clone. Only one of the many clones has her 'soul', the other are pretty mindless and soulless. When the one with the 'soul' dies, that 'soul' just moves to another clone. The organization that possesses the major characters covers it up, presents the new Rei as if she was the same Rei. Yet each appearance has subtly different personality variations. A big inspiration for Hydra/Beta is the sequence showing many Rei clones floating in a fluid-tank, all smiling at you.
Kaworu, the final Angel (the monster-of-the-week enemies in NGE). Where the other Angels appear as eerie alien creatures, Kaworu appears as a boy. A boy the age of Shinji. He is warm and loving, so much toward Shinji that it's frequently interpreted as homoerotic. He gives Shinji the affection he longs for. Kaworu also, like all the other Angels, have the goal of uniting with the Angel in the basement of that organization, to bring around the end of the world and a reinterpretation of it as something more for Angels than humans (presumably).
Okay? You get a sense of those two characters? Hydra/Beta is a mesh of the two. I never realized this until I was describing Neon Genesis Evangelion to Twin's player with the knowledge that she will never watch it and a resulting goal of just getting across what about it affected me.
As well, Neon Genesis Evangelion gave me the 'basic Strange mood' that has run through me countless times since. This mood? The feeling I got when the main character, during his first time piloting his giant meat-robot, gets an image in the corner of his eye of this creepy thing, basically the robot without its covering armor.
More odd influences: Beta's tendency to randomly liquidize or vaporize herself is influenced by the apocalyptic ending where everyone is turned into liquid, leaving only their clothing and a puddle of womb-fluid. In that sequence, they get absorbed into the forming singularity-mind. Beta returns to her own gestalt-mind, again and again every time she destroys herself. How much of that is coincidence? Weird.