Star Trek: Voyager: Season 5, Episode 7

5 - 7: Infinite Regress

Voyager encounters a Borg cube's debris field containing technology called a Vinculum, a device that connects all the drone's minds. The device causes Seven of Nine to exhibit multiple personalities of people she assimilated as a member of the collective, including a Klingon, a Ferengi, a Vulcan, and a human. Soon, they become so strong that they may overwhelm Seven's own personality.