Body-stealing aliens have been a popular trope in science fiction for a long time. However, in the progressive “Star Trek” universe, becoming the host to an alien isn’t something to be scared of — it’s an honor that grants you lifetimes of knowledge.
At least that’s the way the alien Trill see things. On their world, dominant lifeforms are classified into two separate groups: entireoid beings who look very much like us (aside from some fashionable spots), and a race of worm-like alien symbiotes that can physically join with humanoids and experience their lives. Upon death, the symbiote separates from its host and bonds with a new Trill, granting him or her all the knowledge and talents of its previous hosts.
Naturally, this is one heck of a way to enhance your education. Just ask Jadzia Dax (Terry Farrell), a Trill woman with the body of a supermodel and three hundred years-worth of collected knowledge. Incidentally, the Trill don’t segregate between male or female hosts, meaning Jadzia knows exactly what it’s like to be both a man and a woman.
Curiously, while Jadzia typically considers all her previous hosts to be part of her overall whole, some “Star Trek: Deep Space Nine” episodes like “Facets” and “Field of Fire” show Trill can perform special rites that call up the personalities of early hosts, allow them to manifest as ghost-like beings or possess the bodies of others. This “talking to yourself” a whole different meaning.
https://www.looper.com/761669/best-movie-and-tv-characters-who-share-a-body/ Best Movie And TV Characters Who Share A Body