Bumping FTW. But I feel I should clear this all up.
That would be Maeda-kun (Kosaku Maeda). He's credited as MAEDAX in the credits. In Zoku he's known as Maedax G.
He's also voicing that laundry guy at the end of the stalker chain in episode two (maeda cleaning it even says on his clothes) and other random characters in other episodes.
He's an assistant to Koji Kumeta (the creator of the zetsubou sensei manga).
There was a vote before the DVD realeases of the first season about if they should leave the censorship parts with him out or not and it ended with them being removed.
Here's his wikipedia page if you can read japanese or want to run google translate on it: http://ja.wikipedia.org/wiki/前田君