Complex sentence: The creator, executive producer and narrator Shelly Duvall, occasionally appeared in episodes, others including Jean Stapleton, Mark Blankfield, Charlie Dell, Donovan Scott and Daniel Frishman, where among the credited cast who appeared in more than three episodes.
Split into simpler sentences: The creator, executive producer and narrator Shelly Duvall, occasionally appeared in episodes. Others, including Jean Stapleton, Mark Blankfield, Charlie Dell, Donovan Scott and Daniel Frishman, were among those who had credited appearances in more than three episodes.