Urbanite#2:"That's so, Mofo."
Confused Honkey:"What the fuck...oh, they're speaking cockroach."
Similarly, it can refer to an annoying human who seems to be indestructable, yet annoying to those who don't have the ability to annoy themselves.
Recruiter 2: Let's go see......
Army recruiter 1 (again)....... Have you thought about enlisting in the Army lately ???