::::::Okay I looked through the credits in the episode and they list the "stars" at the start and the "guest stars" and "also starring" at the end. This is not how I would define guest stars. I had always thought of a guest star being Michael Jackson or Glenn Close appearing in the Simpsons (well known celebrities appearing in short roles). At least that rules out the original research worry I had after reading the reply above. I still don't like that list, but at least I know where it comes from and it seems consistent with other episodes I found.