I can't comment on the Vegas episode with Doc, because I never watched the show.  But, Doc and Johnny did have a discussion on the Tonight Show that contained some similar comment and/or sentiment.  Now, I suppose it might have been a discussion that included some reference to the show that Doc had "guested" on, but they did have a conversation about MF and his"label" and had a bit of a laugh about it.  The only thing a bit fuzzy in my thirty-five-year-old memory is the exact context of the conversation.