Eon Blue Apocalypse

This thought just arose in my mind, it's just an idea, I don't know whether it has been tried and whether it's actually possible.

How about a special power, granted through a kit, race, item, spell, whatever, where you could approach a creature and take over it's identity, after a winning a battle of will power, discarding your old form. You'd receive the appearence, items and physical stats of the new host, but you'd retain wisdom, intelligence, experience and class. Possibly you could also move about as just a spirit, either because you chose to or because you attempted to ussurp a body the occupant of which proved to strong for you to remove.