Rex209 is a character that makes a cameo appearance in Nitrome Must Die, and appears mostly throughout Test Subject Complete. Rex209 is a suit created by the Professor as a prototype, but was stolen by Doctor Nastidious - the forerunner of the vast mech suits the doctor would later create for attempted world domination in Test Subject Complete. Rex209 plays a major role in Test Subject Complete's story, guiding Blue in decisions to make along with doing much of the investigating in Dr. Nastidious's base. Along with this, it is the first Nitrome character to speak in English outside of text.