Negative Doofenshmirtz, or just Nega-Doof, is the negative version of Doof from the Negative Dimension. He first appeared in Ultimate Power. He was seemingly killed with Doof in Part 3. He has a reversed-color labcoat (white shirt, black coat), with a while outline on the coat, darker green pants, red eyes, and darker brown hair. He also talks "tougher" than Doof. He knows a lot more about the Ultimate Power than Doof. He is rumored to return, but maybe not.