Doctor Mikhail Sergeyevich Cossack

Dr. Mikhail Sergeyevich Cossack (Ｄｒ．コサック)(rus. Михаил Сергеевич Казак) is a Russian roboticist who lives with his daughter, Kalinka. In Mega Man 4, he sent a letter to Dr. Light stating that he has created eight Robot Masters and sent them to take over the world, in order to show the world his genius. Mega Man set out to defeat the eight new Robot Masters, and made his way to Cossack's Siberian fortress. Just as he defeated Cossack, however, Proto Man appeared with Kalinka and revealed the truth: Dr. Wily had kidnapped Kalinka and forced Dr. Cossack to build the robots as ransom. After Mega Man defeated Wily once again, Dr. Cossack built a robotic bird called Beat for him, as a gift for saving his daughter.

Cossack Catcher
Cossack Catcher is the machine that Dr. Cossack uses in the fourth Cossack stage. It's design is based on the UFO prize catchers commonly found in arcades.

Trivia
In the same fashion as fellow scientists Albert Wily and Thomas Light, Master Mikhail of the Sage Trinity in Mega Man ZX was named after him.