How about multiple personalities at Eloise? You got it. Milton Erickson, the famed psychologist who was a pioneer in the field of hypnotism studied a woman named Ellen who had a co-existing personality named Mary. Both were highly functional and seemingly caused the woman no harm with the latter appearing only when the former "went away."
Erickson performed a series of tests along with visiting Dr. David Rapaport which can be read here.