Complex sentence: One of the most notable guest stars of the series was singer/actress Dolly Parton, in the January 1,1990, one-hour episode "The First Day of the Last Decade of the Entire Twentieth Century".
Split into simpler sentences: One of the most notable guest stars of the series was singer/actress Dolly Parton. Parton guest starred in the January 1,1990 one-hour episode "The First Day of the Last Decade of the Entire Twentieth Century".