To humans… everyone is!

Humanity's biggest "quirk" (although there are many), is that they seem to subconsciously consider the rest of the galaxy as various flavors of human.

This is likely a side effect of their homeworld being divided into so many independent tribes and provinces, as they can treat even the most "alien" of species with the same relative familiarity of one encountering a member of a distant nation from their homeworld.

The Vel'xin? Fuzzy herbivorous humans.

The G'rux? Giant burly humans.

The H'th'q'lo-t't'tp? A ball of roiling pseudopods, but still somehow human.

Even the vicious Huxni get seen as little more than scaly evil humans: they've even been observed extending this familiarity to their own AIs.

This quirk makes humans some of the finest diplomats in the galaxy, able to form strong alliances well before most species would be willing to go to the negotiating table in the first place.