Bass was built by Dr.Wily as an attempt to destroy his greatest foe, Mega Man. Based on Proto Man and Mega Man's blueprints, Bass has all of the adaptive abilities of his blue counterpart. Bass was programmed to become the strongest robot in existence, which constantly brings him to face Mega Man in combat.
Additionally, Bass has a robotic dog Treble, the counterpart to Rush.
After several repeated failures to defeat Mega Man, Bass blamed Wily for being too weak and keeping him from attaining his true power. Bass rebelled against Wily and began his own vendetta against Mega Man. However, when Bass noticed a considerable rise in the strength of Wily's machines, he decided to temporarily join up with Mega Man to prevent anyone from exceeding his power. Bass has since been seen in various encounters with Mega Man, all resulting in either a tie or a loss for Bass.