This is a science fiction setting initially inspired by the idea of cyborgs, artificial bodies, and making switching a brain between bodies so routine some people do it for recreation.
To make sure people can recognise each other despite switching bodies, everyone has a unique ID taking the shape of a design built into, or applied to, the face of a humanoid body, or an easy to see location for others. There are both laws and strong taboos against obscuring or faking an ID.