Dr. Doppler is a main antagonist from Megaman X3. He is a Reploid who once worked alongside Dr. Cain in robotics and was the one who discovered the nature of the Sigma virus, leading to him creating a "Cure" using a Neuro Computer as well as a new utopia in his name. The supposed cure was a ruse and was in fact a placebo that would later turn other Reploids into Mavericks under his control. This resulted in an uprising but ended up being due to him also succumbing to the virus as well as he planned to revive the once fallen Maverick leader Sigma.

He appears as an elderly Reploid man with a white beard and hair curved upward. He wears sleek blue and gray armor over black tights plus an open flowing lab coat over the armor. Infused into his shoulders are cylinder dynamos with wires that connect to a head band he wears.

In terms of combat he relies more on defenses, being able to surround himself in a barrier while charging at the opponent as well as generating energy that absorbs energy based attacks in order to regenerate. Using openings in his fingertips he can fired simple electrified orbs.