Complex sentence: Of over three dozen entertainers to join the cast, only Rowan, Martin, Owens, and Buzzi were there from beginning to end, although Owens was not in the 1967 pilot and Buzzi missed two first-season episodes.
Split into simpler sentences: Of over three dozen entertainers to join the cast, only Rowan, Martin, Owens, and Buzzi were there from beginning to end. However, Owens was not in the 1967 pilot and Buzzi missed two first-season episodes.