Pretty sure there visually isnt any, which is why they are forced to wear black ribbons on their eyes during the Ball, so that people can distinguish between homunguli and the guests. Outside of those areas they are always in uniform or in their own spaces anyway, so its easy to distinguisb
so a homunculus could pretend to be human and the humans wouldn't know, correct? If so, couldn't the homunculi do that and take over that way?
No because they've got the mass-brainwashing thing happening rn. Once the ML awakens his King of Homonculi power it will override the imperial family's brainwashing but before that there is nothing they can do even if they blend in with humans
how it is possible to tell the difference between a human and homunculus especially at first glance?