When Ralph goes from Hero's Duty to Sugar Rush, he brings a Cy Bug, a destruction machine villain from Hero's Duty. It has an advanced AI and doesn't know the game turns on and off like everyone else. Once that happens, Calhoun and Felix team up to clean it up as it could be end of the arcade. The look of the Cy Bugs vary but think of a beetle with vials of fluid on top of it. And yes, it's acid green.
