TWO DIFFERENT CASTS?

Were there two different cast groups on gilligans island?
When was Gilligans Island first started?
I heard there was an original cast, but new people came on the show in "64"

There was a different cast used in the pilot for the professor, mary ann, and ginger.. they were actually known as Ginger, The Professor, and Bunny, and were played by Kit Smythe, John Gabriel, and Nancy McCarthy. It aired in November, 1963 and was filmed in Hanalei Bay on the north shore of Kauai, Hawaii...