Tuvix was a unique individual created through a transporter accident aboard the USS Voyager.
He was a hybrid of Lieutenant Tuvok (Vulcan) and Neelix (Talaxian), along with an alien orchid.
He retained the memories and some personality traits of both Tuvok and Neelix, but was a distinct person.
He served as an officer on Voyager, combining Tuvok's skills with Neelix's culinary talents.
Tuvix valued his existence and wished to continue living.
He was played by actor Tom Wright.
Tuvix was tragically and unjustly ended when Captain Janeway made the decision to forcibly separate him back into Tuvok and Neelix, against his expressed will to live. He was, in effect, murdered by Captain Janeway.