The Mizarians were a humanoid species native to the planet Mizar II. Mizarians valued peaceful non-resistance over confrontation; because of this reputation, they were conquered six times in a matter of three centuries. The Mizarians survived these invasions by offering absolutely no resistance. Kova Tholl claimed that the Mizarians were a species known for possessing superior intelligence. (TNG: "Allegiance")
List of Mizarians
According to an internal reference document, listing all the aliens seen in Star Trek: The Next Generation, which was circulated around the time of the production of TNG Season 5, the Mizarians were given the description of "a highly intelligent and pacifistic race, humanoid in appearance buy with whitish facial skin sharply folded along vertical rather than horizontal lines above and below the eyes."
Michael Westmore once commented that a typical Mizerian looked "almost like a villain from Dick Tracy." The elaborate hood often seen atop a Mizarian's head led the TNG makeup crew to nickname one of these aliens (namely, Kova Tholl) "The Sydney Opera House Head." (Star Trek: The Next Generation Makeup FX Journal, p. 65)