Possession

Possession was the magical process of one thinking creature taking over another one's body.

Most spirits in the Prime Universe were capable of possession, and possessing sentient beings from a universe other than the Prime would allow themselves to “anchor” themselves to those universes, being able to linger there beyond Halloween. When the Great Ghost and his legion escaped the Spirit Realm on Halloween 2019, they possessed a great number of beings including the Gang of the Green Gorilla and some of Madame Tarsa's magical marionettes. The Great Ghost himself chose the Queen of the Black Market as a vessel, prompting her to remark rather casually: “My third possession in fifty years. I have got to invest in a couple of sturdy warding amulets”. (PROSE: The Ghosts and the Machine)

In the 89067986779811167562948736197891674912223184th Universe, going back along the Doctor's timeline, the Great Intelligence possessed a TARDIS which it believed the First Doctor would try to steal. (PROSE: How To Steal Timeships & To Influence Time Lords)

Sophie Everytime once thwarted one of her her aunt's schemes by possessing Jenny Nowhere's body at a critical moment. Her father was very proud of her doing this at such a young age. (PROSE: Family Business)