The GUEST who posted on 22-Apr-02 - 10:41 AM said: "If you go to http://us.imdb.com/Name?Morris,+Greg+(I)#guest you will find a list of every TV guest appearance that Greg Morris made since his debut in 1959."

That is incorrect. The heading in that list clearly states "Notable TV guest appearances", so not every guest appearance is listed. If Morris did appear on the Andy Griffith Show, IMDb must not have considered it worthy of note.