Doctor Nefarious is the antagonist of the Ratchet & Clank franchise. He is an organic lifeform transformed into a robot and archenemy of Captain Qwark, Ratchet and Clank. He first appeared as the main villain of the 2004 game Ratchet & Clank: Up Your Arsenal before returning in 2009's Ratchet & Clank Future: A Crack in Time.
Arthur Nefarious has created Ameboids at Blackwater City, Rilgar to wreak havoc towards Captain Qwark. Qwark followed him to Magmos, where he fell down a machine that transformed him into a robot. He later attacked Metropolis of the planet Kerwan with his insects before he got disassembled. He was found by his robot butler Lawrence to capture Qwark in his secret prison. Years later, Nefarious would begin a campaign against organic life-forms. He hired famous pop star Courtney Gears to spread his message towards fellow robots.
Armin Shimerman has voiced Nefarious since his first appearance.