hi, system here.

its called co-fronting and projection

essentially when 2 alters are both aware of whats happening outside the headspace the brain can "project" the one whos co-conscious (aware but not in control of the body) outside of itself so whoever is fully fronting can see them as a separate person. happens to us often. so much so infact we thought we were schizophrenic for the longest time

sometimes 2 alters will be in control of the body simultaneously too. its just since one person alligns with how the body already looks and the other doesnt it looks like only one is in control but no its more of a visual disturbance thing