What does starting a reply with "Grunch" mean?

[DarkForceRising]

I've been spending a lot of time reading the Limit-->NL forum lately and I notice many posters starting their replies like this. I have been paying particular attention to advice given by Grunch, as he is always clear in his analysis. Nor does he appear to engage in any silliness.

So what's the joke/reference here? TIA