Now look at this, from a February 16th, 2007 IGN interview with Jack Coleman who plays Mr. Bennet a.k.a. HRG:
Question: I think the funniest fan speculation I've seen is that Mr. Muggles is going to turn out to be a shape shifter or something.
Coleman: I did read that Mr. Muggles was Linderman which I can tell you he's not. I'm going to put the kibosh on that rumor right now. Mr. Muggles is not Linderman... Mr. Muggles is Sylar. [Laughs]
Admittedly, after seeing this past week's episode I'd already pretty much dropped my theory about Mr. Muggles being anything special. But to have come up with a theory so wacky that it actually made it to the attention of TPTB is a nice little propeller in my fandom beanie, I must say. If it's true.
*waits for someone to come along with a link to a post suggesting the same theory that predates my comment on TWoP, and therefore proves that I am not special after all*