All I really remember is the wide brush strokes of how in the earlier seasons the Island was more grounded in reality with things like "movie special effects", etc. and Roarke would be shown to be playing some of the characters the visitors encountered, but in the later seasons Roarke was some kind of supernatural creature and occasionally fought demons and crap.
In the last season (I think it was the last season), Roddy McDowall played the Devil, and he and Roarke contended for the soul of Roarke's young female ward (I forget her name). Finally, Roarke offered to split the difference, saying the Devil could have her 3 days a week, he'd have her 3 other days, and she would get 1 day to herself. The Devil said, "That's absurd!" and somehow the situation got resolved.
I remember enjoying these shows a lot - Saturday night was the Love Boat/Fantasy Island time, and a lot of actors guested on both shows. There were even a couple of crossovers, although Mr. Roarke never stepped foot on the Pacific Princess.