Here's a Toobworld theory by Gordon Long, which was passed along by Christofer Nigro, the major domo of the shared universe known as "Wold Newton Beyond":
|"GILLIGAN'S ISLAND" PILOT|
The Skipper with Ginger, the Professor, and Bunny
On the OTHER 'Gilligan's Island', the one seen in the pilot (which is not in the primary Toobverse or the TVCU, since it was not aired until decades after the series ended) with a different 'Professor' (actually a hunky high school science teacher) and two secretaries Ginger and Bunny (only the Skipper, Gilligan, and the Howells were the same) is actually ANOTHER island with castaways.
In one first season episode, the gang hears on the radio that the crew of the SS Minnow was sighted and would be rescued soon....only to find out it was a different SS Minnow, on a different island--and they'd been marooned for 11 years!!!
I believe that the rich couple on that island is actually the Powells. In another episode from the second season, they hear via the radio that the entire Howell fortune is gone---causing Thurston much angst---but at the end, hear that it was really the Powell fortune. I think that the Powells were out of touch with civilization so long, that not long after they got back, their fortune crashed.
Another part of the hypothesis has it that Gilligan and the Skipper from the pilot are related to the Fearless Crew that we know and love. And that would work in a Patty Dukish "identical cousins" kind of way. It's accepted that the series Gilligan's first name was Willy, so the Pilot Gilligan could have any other first name. Likewise, the Skipper of the Series was Jonas Grumby, while the Skipper of the Pilot doesn't even have to share the same last name.
As for the other Ginger, she was a secretary not a movie star so there's no problem there.....