It turns out that the humans we had been receiving with mostly open arms were in fact, not average humans. They've been mostly military, or at least military-related, with baseline modifications, and more or less on best behavior. Take a moment to comprehend that statement. The man that accidentally turned a moon into an expanding ball of plasma was a military engineer on his best behavior, working without our civilian-grade weaponry. Yeah.
It turns out that human cybernetic and genetic technologies are further along than we thought. They've figured out some way not only to selectively kill and regrow cells in accordance with new genetic code but managed to get their neurons to replenish themselves and flawlessly integrate with existing nervous structures. Because of this, humans can change their bodies like those of us with tattoos would change them. It's not something done in a couple of seconds, but it's hardly arduous.
Because of this, many have modifications that are far from their baseline enhanced intelligence, strength, durability, etc, viewing altering their body the same as we view changing pants. For the species that don't wear pants, you get the idea.
As such, you will likely be seeing humans with soft fur, scales, tails of whatever type, wings that shouldn't be able to support their mass but do, claws, feathers, bigger ears, more limbs, different eyes, digitigrade legs, differently proportioned limbs or bone structures, or any other number of modifications. Basically, if you see a sapient species you don't recognize, odds are decent it's a human. There also might be some humans with bodies closely mimicking some of the more, to them, cute, of us. To quote one human "Oh my Omnissiah, those squirrel people are so adorable!" To them mimicry is among the greatest forms of flattery, so try not to be too offended. Every species has its... quirks.
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Since some people would freak out when a human's hair dye would fade, (that was an interesting discovery, though some have taken up the human idea of dyeing parts of their bodies) if your human coworker/compatriot/whatever shows up one day looking entirely different, don't freak out that they're dying or have a disease or something.
Proclivity for bodymorphing aside, be aware that from this point the humans you'll mostly be interacting with aren't as dead-set on making a good first impression, which we are told means they'll be tamping down on their creepier instincts less. When we asked for clarification on what they meant their body language shifted to be almost motionless when not actively changing position and far more snappy and precise when moving, and a swarm of tiny drones flew out of their torso. Some buzzed around them in a manner that was disturbing for reasons we still can't discern while other drones observed everything and everyone nearby from various angles as if deciding how best to disassemble such for information on its workings. That combined with them greeting people before they were visible or audible and several other things resulted in us requesting they go back to as they were not long after.
Still, it seems that overall personality remains the same between the two groups, if rather amplified in nature in the second. Sure, this means that the lack of empathy for those they deem an enemy is even more pronounced, but so is kindness. Just, be aware that the humans being extreme in everything holds even more true.
Oh and we've been informed that our previous document was wrong, those weren't military-grade weapons, just slightly higher-end civilian.