Jay Johnston (voice of Mr. Goodman and other characters on Mr. Pickles) was a writer and recurring character on Mr. Show with Bob & David (1996-1998) and has returned to do the same for the new Netflix show "w/ Bob & David" (2015). He was also a writer and voice actor for the religious parody stop-motion animated series "Moral Orel" (2007-2008).
In the opening of Mr. Pickles, you can see one of the townsfolk where a little kid with a green shirt has a face mask logo which came from Will and Dave's vanity card. And it is also shown at the end of the credits.