There's a lot of speculation that the One With The Markings is that Bill Roberts ("INK") from the TiVO'd news clip, but I think there's another potential candidate that is being overlooked.
How about the professor from Michael's class in the first episode? We have been told that the smarter you are, the smarter the zombie you would become, so a zombified professor would be a good candidate for a super smart zombie to rule them all.
Also KC voiced the professor and also provided the zombie calls. It would be a nice bit of continuity to have the same individual record the One with the Markings before and after he became a zombie.