One of my fellow tumblrers pointed out that many of the answerers did not actually give me the name of the legendary lyricist I was asking for.
The legend is SHOCK G. So in fact, just one of you got it. Well done, David! (And by the way, which David are you?)
Ah, another addendum thanks to Matt who might now be my future husband. The other writers of the Humpty Dance are George Clinton, Bootsy Collins, and Walter Morrison.