Gilligan's Island tells the familiar tale of a group of unlikely castaways stranded on a deserted island. The ship's captain ("the Skipper"), his first mate, a movie star, a millionaire, the millionaire's wife, a professor of an unnamed discipline, and some random woman named Mary Ann. The castaways have numerous adventures on the island, highlighted by frequent hijinks.
While the viewer is meant to take the story as a simplistic comedy, upon deeper inspection the story begins to unravel and it becomes clear that all of the characters and set pieces are simply the hallucinations and fantasies of the Skipper.
Some may ask, "Why the Skipper?" The Skipper is the only character on the show, save Gilligan, who's presence on the island actually makes sense. Why would any of the other characters have decided to take a "3 Hour Tour" on the Skipper's crappy little fishing boat? What is far more likely than all of these random folks deciding to hop aboard the S.S. Minnow is that they are figments of the Skipper's imagination designed to counter his raging inferiority complex.
The Skipper is a troubled angry little man. Even in the show, which is merely his hallucination, he is prone to childlike temper tantrums. He is an older single man who is out of shape and has to rent out his fishing boat for tours. His best years are clearly behind him, and he has amazingly little to show for it except a crappy boat and a stupid hat. He's an almost tragic figure and the ideal candidate to have a massive inferiority complex.
One day, perhaps in a drunken rage, he crashes his boat onto a deserted island. He then proceeds to imagine a group of unlikely companions. In his mind, these rich, famous, and intelligent people likely came aboard his stalwart vessel because he was the world's greatest sea captain. Once the group has crash landed onto the island, they come to rely on him and look up to him as the leader of their faux community. For a person with an inferiority complex, this sudden influx of power and respect, especially from such well to do members of society, would be a great boon.
The presence of Gilligan makes sense in this context as well. Gilligan is the Skipper's imaginary foil, designed to make the Skipper look even better in comparison. Every time Gilligan bumbles, the Skipper can swoop in and save the day, thus further proving his superiority to the other imaginary castaways.
The series' ending also makes sense in this context. In show's last episode, the castaways are rescued, but end up returning to the island after discovering they preferred island life to life back in the real world. This ending makes no sense for characters like the millionaire and his wife, who went from a life of great leisure to eating nothing but coconuts and relying on a bicycle made out of bamboo for power. But it does make sense if the Skipper is the only actual character. Upon returning to the mainland, the Skipper is thrust back into the harsh reality of being an outsider and a loser. This is a stark contrast to the "life" he had built for himself on the island where he was a confident and desirable leader of a community. The Skipper heads back to the island, so he can continue to live in his perfect fantasy world, rather than continue a life he was unable to deal with in the real world.
Or I could be reading entirely too much into that...