Dr. Robotnik goes on vacation but cannot resist scheming — this time building an army of robotic Mario copies to execute his latest plan for world domination. The robots eventually break free of his control and turn against their creator.
With his machine army in revolt, Robotnik pivots to feline muscle, assembling a new force of cat henchmen commanded by the ruthless Captain Robocat. To counter the threat, Sonic must team up with the rogue Mario robots, leading them in battle against Robotnik's cat army and ultimately facing Captain Robocat in a final showdown.