Being created when a transporter accident fused Tuvok and Neelix, who pleaded for his life when Janeway chose to separate him.
Tuvix was created when Tuvok and Neelix were beamed back from an away mission together with a symbiogenetic alien orchid, which merged their patterns into a single person. Played by Tom Wright, he combined Tuvok's discipline with Neelix's warmth, served as the ship's cook and an officer, and won friends among the crew.
When the Doctor found a way to separate the two, Tuvix refused, arguing that he was an individual with a right to live. Janeway overruled him and escorted him to sickbay herself, restoring Tuvok and Neelix in one of the series' most debated decisions.