Doctor Nastidious is the antagonist of the Test Subject series, appearing in the Test Subject games Test Subject Green and Test Subject Complete. He also appears in the background of several levels of Test Subject Arena and as a playable character in Test Subject Arena 2. Doctor Nastidious is a green skinned scientist who is much like an evil version of the Professor, responsible for raiding Xeno Industries and performing tests with the Professor's equipment in his (Dr. Nastidious's) own base.