Faces, VOY 1
Those creepy organ hunters the Vidiians are back. By now everyone should know: stay out of caves! Anyway, B’elanna Torres is split in two. Much like Kirk got beamed back half good/half bad, Torres is somehow gene spliced into half-Klingon half-Puerto Rican. Philosophical questions about consciousness, self and identity aside, the two must work together is part ass-kicker, part computer-tapper to escape. But not before Chakotay shows up dressed as Leatherface.
The Doctor is somehow able to get the DNA from dead all-Klingon Torres into living no-Klingon Torres. He does this with only about 30 seconds left in the episode, so we have to trust that it worked out okay.