"Functionally retarded" would have needed too much space
I think when this guy was asking folks to "Git-R-Dun" he had Eddie Hazel in mind. This is one of the best solos in music. The story goes that while George Clinton was on acid he asked Eddie Hazel, who was smacked out on heroin, to play the first half of the song as if he had just found his mother dead and the second as if she had risen again. Oh yeah, he also did it in one take.
Let's see what you "git-dun" today.