A member of the Vissians' third sex who learns to read and think for itself after Trip Tucker takes an interest.
Charles is a cogenitor, a member of the Vissians' rare third sex, needed for reproduction and kept by a Vissian couple with few rights of its own. In Cogenitor, Trip Tucker secretly gives it books, music and films, teaches it to read, and gives it the name Charles.
Awakened to a wider life, Charles asks for asylum aboard Enterprise. Archer refuses, judging that Starfleet cannot interfere in Vissian society, and the cogenitor is returned. Charles later takes its own life, leaving Tucker to face the cost of his good intentions.