Dr. Doppler

Dr. Doppler (Ｄｒ．ドップラー) is one of the main antagonists of Mega Man X3. He was the first Reploid scientist, and was very well known. Early in the story of Mega Man X3 he claimed to have created a vaccine to the Maverick virus, and he also created Dopplertown. Unfortunately, it soon turned out that the "vaccine" was a placebo, and Mavericks started to pop up everywhere. Thanks to Dr. Doppler's "vaccine" more Mavericks were created. Doppler then became the leader of the Doppler Army, an army comprised of some of the most powerful Mavericks the world had ever seen.

Later on in the story, it is revealed that Sigma took control of Dr. Doppler and forced him to create a new battle body for him. He also rebuilt Vile and hired Bit and Byte of the Nightmare Police to destroy X and Zero. You fight Doppler at the end of Doppler stage 3 and his weakness is the Acid Burst. After his defeat,he tells X about Sigma's new body and where to find it.Dr. Doppler's fate depends on whether or not Zero is still active. If Zero is still active, Zero comes in to delete the Sigma virus (which failed as Sigma is alive and well in X4). But if Zero had to go back for repairs, Dr. Doppler makes one last move and self-destructs, taking Sigma down with him. In the former ending, Doppler's fate is never revealed, although he did give Zero the anti-virus needed to finish Sigma.

Trivia

 * As with Mega Man X4, fans like to debate which of the two endings is the canon one, since there is no solid indication in the series. While Dr. Doppler hasn't made an appearance in subsequent games, his anti-virus technology seems to live on, most notably in Mega Man X5.
 * Dr. Doppler seems to have been named after the Doppler Effect.
 * Dr. Doppler bears some resemblance to Dr. Weil.