Dr. Cossack sent a letter to Dr. Light stating that he created the eight Robot Masters and his robots are reprogrammed by Dr. Wily and Mega Man was set out to defeat his robots and made his way to Cossack's Siberian Fortress. After Mega Man defeats Cossack, Proto Man appears with Kalinka and revealed the truth that Wily kidnapped her and force Dr. Cossack to build the robots as ransom. After the defeat of Wily, Cossack builds a robotic bird named Beat for Mega man, as a gift for saving his daughter.
The Cossack Catcher is an invention that Dr. Cossack uses in the final stage of his castle. It was designed to resemble a prize catcher commonly found in the arcades. Mega Man must use Dust Crusher or Wire Adaptor to do some damage. As the claw is about to catch Mega Man, he must slide to avoid the grabbing and use many Wire Adaptors. Defeating him will make Kalinka come and warn Mega Man to not kill her father. He is not actually evil.
In Ruby Spears' Mega Man, Dr. Cain bears a slight resemblance to Dr. Cossack.