First appearance of Rush, Mega Man's canine companion.
First appearance of Proto Man, Mega Man's troubled brother.
First game where Mega Man can slide.
The ending includes a list of robots created by Dr. Light, along with portraits. It even states what each robot was created for (this includes the Robot Masters from Mega Man I (NES), and Roll, Mega Man, and Proto Man.)
The Doc Robots all have abilities from the Robot Masters in Mega Man II. Every Mega Man II Robot Leader is represented through Doc Robot.